The Count of Monte Cristo begins with a reasonable group of six or so...then fast-forwards twenty years to when each of them has his own distinct family and social circle. There are at least 38 named characters. Wikipedia has a nifty flow-chart showing their relations to each other. (Spoilers, obviously.)
Webserials often have buttloads of characters, as many are long runners with epic lengths. There are plenty who make full use of this trope.
The Gods Are Bastards focuses on several different casts and juggles them. There are an incredible number of minor characters who reappear with plot importance when appropriate and but the arcs are tightly contained. While plotlines intersect often, the main characters of the arc have the limelight with the others as support, with which is which switching around often.
Legion of Nothing has nine 'main' characters, the ones that were around at the formation of the New Heroes League. However in different arcs some are put on a bus for an arc or two, with only the protagonist Nick as a constant, allowing for different members to shine. Sometimes there are other heroes who join the fray, becoming part of the cast of recurring party members.
Eric Flint's 1632 series has 357 pages of character names, for a census of a town. Most of the names have, as yet, not been used for characters which have actually been written, as the series is a collaborative effort and all you have to do is to contact The Powers That Be and ask them to let you write about one of the as-yet unused characters.
Also, basically every important person alive in 1632 in Europe has been used, along with historically unimportant folks by the hundreds. You don't even need to contact the Powers That Be to write stories featuring random peasants or merchants, because there's literally millions of those. The only reason there's a 357-page list is because there was a need to put an upper limit on the number of up-timers.
And Ladies of the Club, by Helen Hooven Santmyer, covers over 50 years in a small town. The eponymous Club starts with six members, then grows to 14, and by the end of the story, all original club members have died and been replaced. And the author goes into much detail about every single person in every club member's family. And their friends who aren't in the club. And their husbands' business associates. Oh yes, and the occasional real-life political figure. It becomes very confusing reading after a while.
While Khaled Hosseini's first two books mainly focus on a handful of characters, his third novel And the Mountains Echoed has seven chapters describing the lives of seven different characters and ALL of their relatives. This graphic only begins to describe the complexities of the relationships in the novel.
Animorphs: Let's see: Jake, Marco, Cassie, Rachel, Ax, Tobias, David, Tom, Eva, Peter, Loren, Naomi, Jordan, Sara, Chapman, Erek, Visser Three, Visser One, Toby, Jara Hamee, Mr. King... And none of those are one-shot characters, either.
In The Baby-Sitters Club series there are many, many minor and background characters who changed with every book.
Battle Royale starts with forty-two students, most of whom get their own backstory.
Betsy-Tacy has dozens of characters - not surprising, considering it follows almost 20 years in the life of a friendship-driven extrovert.
The first Bravelands book alone has a large number of named characters. This is due to the fact the main characters are from three different species of group animals, and thus their families are named as well. Most of these characters play some level of a role.
In A Brother's Price, there are the Whistlers, a family with more than thirty children. Most of them appear in the plot. There's Jerin, Corelle, Kai, Alaric, Blush, Summer, Eldest, and a bunch of toddlers, all named. Then there are the princesses: Rensellaer, Odelia, Trini, Lylia and Halley, and their five younger sisters. And that's only two families. The Whistlers have a family branch that lives in Annaboro, and has lots of members, too. And then there are the families of minor characters ...
Catch-22. 42 chapters, almost all named after characters, and only four are repeats. But that hardly scratches the surface. About half the characters don't have names, so you have Nately, Nately's father, the old man who reminds Nately of his father, Nately's whore, Nately's whore's kid sister, and so on.
A key reason Charlie and the Chocolate Factory takes so long getting to the factory itself is because it's establishing so many significant characters: Pinball Protagonist Charlie and his family (his parents and both sets of grandparents), and then the four other Golden Ticket finders and their families. Counting their guide Willy Wonka, the final tour group comprises fifteen characters. Of course, it's not long before it's a non-fatal Dwindling Party, but budgets and availability being what they are, just try to find an adaptation that doesn't change the detail that a ticket finder can bring up to two family members with them to one and demote several parents to extras — or even drop them altogether.
In the French-Canadian fantasy series Chevaliers d'emeraude (Knights of Emerald), there is a new generation of apprentice knights with nearly every book (there are twelve books), and since the books cover enough time for the young knights to gain their own apprentices in the next book, they grow exponentially. By the 11th and 12th book, there are 10 pages which are a list of all the young knights.
The Chronicles of the Imaginarium Geographica: OH MY GOD! These books have so many characters, you'll need a cheat sheet to deal with it all. You've got the Caretakers, then you've got society members, the rogue Caretakers, the talking animals, the dragons, the ancients, and various other famous characters and people from history. The easiest ways to deal with it all is to either just deal with it as you go, or to keep a cheat sheet for all the characters present.
In the Chung Kuo series, there is a well-needed character list at the beginning, starting with the second novel.
Cloud Atlas features six stories that take place in six different periods of time, each with its own principal cast. Needless to say, it ends up being quite a lot.
Jim Butcher's Codex Alera has about six main characters, with a supporting cast of at least a dozen repeating fairly major characters. Most of the books in this series are split into two or three plot threads, tracking the various endeavors of each of the groups of characters.
Honoré de Balzac's La Comédie Humaine series has the combined cast of 2472 characters, at least 40 of which appeared in more then one novel.
Mystery fiction writer Michael Connelly published his first novel in 1992 and has been putting out books more or less annually ever since. About two-thirds of them star the same character, detective Harry Bosch, and more importantly, all of them take place within the same fictional universe. Thus there are Loads And Loads Of Characters by default, as major and minor characters repeat in novel after novel.
Mark Z. Danielewski:
House of Leaves: By way of multiple literary agents and scrapbook storytelling it's able to cram an impressive array of characters on multiple levels of narrative into its plot. The grand majority of them have a one-shot presence as an academic commentator on the film in the book or a one-night stand with the protagonist Johnny Truant outside the book, but many are referenced again later on as the narrative(s) continue. Even many Real Life people - like Stephen King, Steve Wozniak and Camille Paglia - are featured as characters in the book.
The Familiar: Takes this Up to Eleven - with it having no less than nine narrators and a giant scope across the world. As the series progresses, the character's story-lines start to intersect more, so it pays to take note of all characters mentioned, since they might be introduced in one narrator's story-line but then pop up in another's.
Sherrilyn Kenyon's The Dark Hunters series (including the Were-Hunter, Dream-Hunter, and Chronicles of Nick books which all take place in the same 'verse as the Dark-Hunter books) has so many characters that it can get hard to keep them straight if one isn't a devoted fan who's read from the very beginning. Not surprising since there are over twenty-five books, each focusing on a different couple and all the assorted minor characters they bring with them, along with reoccurring characters through the entire series. And that's not even counting the hundreds of gods, goddesses, demigods, Chthonians, demons, Daimons, and so forth.
The Den of Shadows series usually has an entirely new set of characters for each book, although there's almost always a mention or appearance of a character that appeared in a previous book or will appear again in a later book.
Much of the best work of Charles Dickens features this trope. In Bleak House the count hits thirty by Chapter Ten; Great Expectations is comparatively restrained, with only eighteen distinct characters in the whole book.
The author even once said that it's the overpopulation that may one day kill the series.
And then you realise that apart from Ankh-Morpork, and Lancre, most of the world hasn't been touched, and most of those bits we have seen have had only a brief appearance (the Counterweight Continent and XXXX have had one book each).
The English translation of Doctor Zhivago by Vintage Classics has an introductory "Principle Characters in the Novel" list that gives the names of 24 people, but that's still not the full scope of all the characters who end up important to the plot. It can be even harder for non-Russian readers to keep up with all the proper names, diminutives and occasional aliases that get swapped around for even individual characters.
Dragon Jousters ends the first book with a mere seven named characters. The next book introduces a love interest, her family, eight new riders, all their dragons, a mage for the group, enemy mages, a rider's sibling, and two other love interests. It only gets worse, and the writing starts to suffer.
Just try keeping the scores of dragonriders (and their dragons!), harpers, Lord Holders (and their spouses and kids!), weyr ladies, and various other characters straight in Anne McCaffrey's Dragonriders of Pern series. The abbreviated names don't help either, they tend to blur together, and several have even been subject to Name Drift.
The Dresden Files has a lot of recurring characters as both allies and enemies of Harry, almost all of them Chekhov's Gunmen. Sometimes, outside the main cast, no mention will be made of them for several books at a time, and they're called in to help every so often.
The Faith for a Romance Novel is massive, making it rather surprising for a reader expecting a nice easy read, often requiring a look at the family tree to remember which husband or wife is which for a while.
The First Dwarf King introduces dozens of characters in the first book alone. Books 2 and 3 introduce even more.
Glory in the Thunder has a good seventy or so named characters spanning 6-7 countries, many of them posthumous. An index can be found here. It gets even more confusing when you consider that some characters are Artificial Humans created from other characters, but not the same people.
D. D. Webb's The Gods Are Bastards has more than twenty-five plot-relevant, distinctly motivated characters as of Book 7, and easily twice as many less relevant ones who still have names and personalities.
In Gone by Michael Grant, the list of people alive in Perdido Beach is at 351, and at least sixty names come up on a regular basis.
By the end, 136 of the people in Perdido Beach are dead.
Margaret Mitchell's Gone with the Wind has about 30 main characters and many more named secondary and one-off characters.
The Green Ember has several characters in the first book alone, and the cast continues to grow with each novel to come out afterwards. While there are only roughly three to four main characters in each book, the main cast constantly runs into large groups of characters during their adventures, and they quickly become part of the recurring cast for the rest of the series (or until they're killed off).
Peter F. Hamilton tends to put an absurdly large amount of major characters in his novels, which tends to be why they end up as doorstoppers.
J. K. Rowling has actually stated that she intentionally fleshed out 40 or so classmates (10 in each house in Harry's year plus presumably some that are not in Harry's year like Luna Lovegood and Katie Bell) before she even started writing.
That's not even counting Beauxbatons and Durmstrang students and staff, ministry members, Muggles, student family members, Order of the Phoenix members, Hogwarts staff, Death Eaters, or non-human characters like Buckbeak or Dobby. This is all shown off nicely in the glorious end battle in Deathly Hallows.
Jim Dale, who recorded the American audio books of the series, did 134 different voices just for Order of the Phoenix, earning him a Guinness World Record for creating the most character voices in an audio book. He later beat his own record with Deathly Hallows, for which he did 146 voices.
This is the primary reason why there is so much Demoted to Extra in the movies. When there are ten zillion supporting characters and each book is pared down to a two and half hour film, inevitably some "regulars" will only get a Mandatory Line per movie if that.
Homer is probably the patron saint of this trope. Both in The Iliad and The Odyssey you have dozens of major characters and what seems like hundreds of minor characters - many of whom appear in both epic poems - including most of the Greek gods and goddesses. And usually even the minor characters are named and come with a background; thus in The Iliad even "small-fry" warriors who just walk on to be slaughtered by the big-name heroes generally come supplied with the name of their father and information on the place in Greece or Asia Minor where they're from. And there's no One Steve Limit either...
If you read Egill Skallagrimsson's Saga, you soon notice that a good half of the characters are named after Thor. When said character die, his family and friends tend to name their kid after said dead character.
The Illuminatus! trilogy has at least three main protagonists (and possibly more), each of whom has their own supporting cast, with only a few overlaps. Just try to try and keep track of all of them on your first read through without taking extensive notes.
The Infected has eight POV main characters, and over seventy secondary and minor characters, a few of whom have their own character arcs.
Each book of the Jeżycjada series by Małgorzata Musierowicz has a different protagonist. These protagonists all live in the same city, in the same district, many of them were at school together, they all have families who are characters in their own right, so the cast was already huge well before the series got 20 books long.
A good deal of Stephen King's work falls under this trope, especially since a great number of his books and stories are within the same universes as each other.
The Stand contains sixteen to twenty main characters (heroes and villains) whose inner lives we follow, and dozens of supporting characters. As a result, the book switches to different story arcs in different parts of the country several times in each chapter..
Several of his stories, including The Tommyknockers, Needful Things, and Under the Dome, follow the lives of a town, and he spends whole chapters introducing characters he will just kill off later. In fact, of these three books, Needful Things is the only one where he doesn't Kill 'em All, he only kills half the town in that one.
Each book in the Kushiel's Legacy series by Jacqueline Carey has an index of characters running four or five pages long.
L.A. Confidential. The already complicated movie contains maybe 20% of the book's story. Ellroy's other books feature it as well, but none to quite that level.
The characters featured in the movie The Wizard of Oz are only a tiny fraction of the overall Land of Oz cast. There are dozens of important non-movie characters in the 40 books of the canon (yes, there's a canon), like Princess Ozma, Tik-Tok, Polychrome, and the Patchwork Girl.
The Legend of the Ice People inevitably has this, as it follows a family for several centuries. Comparatively downplayed because of how few children the Ice People gets, however.
J. R. R. Tolkien's The Lord of the Rings. Frodo, Sam, Merry, Pippin, Gandalf, Aragorn, Arwen, Elrond, Gimli, Legolas, Boromir, Faramir, Denethor, Gollum, Théoden, Éowyn, Éomer, Bilbo, Galadriel, Saruman, Gríma, and Treebeard all have their pictures in the ending credits of the film version. And then there's plenty of more minor ones, such as Gamling, Haldir, Celeborn, the Witch-King, Gothmog, and Isildur. Oh, and Sauron.
The Silmarillion is worse than The Lord of the Rings, and rightly so in that regard, as it covers more time of the history of Middle-Earth. In the first forty pages alone, you have Eru, the fourteen Valarnote Manwë and Varda, Ulmo, Aulë and Yavanna, Námo (Mandos) and Vairë, Nienna, Oromë and Vána, Irmo (Lórien) and Estë, and Tulkas and Nessa and Morgoth. And then, in the main part of the book, you have around another thirty or so main characters fighting for the limelight, including Fëanor and his seven sonsnote Maedhros, Maglor, Celegorm, Caranthir, Curufin, Amrod and Amras, Ungoliant, Thingol, Melian, Húrin, Túrin, Niënor, Fingolfin, Finarfin, Finwë, Galadriel, Sauron, Carcharoth, Beren and Lúthien, Eärendil, Finrod, Morwen, Huor, Gothmog, Indis, Fingon, Turgon, Eöl and Aredhel, Idril and Tuor, Glaurung, Glorfindel, Elwing, Bëor, Haleth, Angrod, Aegnor, Orodreth, and Gil-galad. Half of these characters end up dying a couple chapters after they're introduced. E.g.: Fëanor didn't live long after he left Valinor, Glorfindel only shows up for a couple pages, Beren and Lúthien are hardly mentioned after their tale is finished, etc. To be fair, The Silmarillion wasn't exactly intended to be a novel, and the history of Númenor and retelling of the story of the One Ring are really separate stories (with their own characters) that just happen to be published in the same volume.
To make things worse, many of the characters are known by more than one name. For just a few examples, Finrod is also called Felagund, Túrin is also called Turambar, and Thingol is also called Elwë. On top of that, many of them also have special names for their horses, swords and in some cases even helmets.
The Hobbit has much fewer characters than either of the two above examples, but 15 distinct main characters is still a little much for one rather short book; along with Bilbo and Gandalf, there are 13 Dwarves to remember (Dwalin, Balin, Fíli, Kíli, Dori, Nori, Ori, Óin, Glóin, Bifur, Bofur, Bombur, and Thorin) plus minor characters such as Gollum, Bard, Elrond, Dáin, Beorn...
Steven Erikson's Malazan Book of the Fallen series fits this trope. Each book has about four pages devoted just to listing the characters that appear in it. Book onw throws at least 100 names at you to remember as well as an INCREDIBLY complicated (and intentionally not very clearly explained) backstory, and then Book two introduces a whole new cast the same size... This goes on up to and including the final book. Additionally, the list of characters in each new book is more a representative sample of important names, and in no way exhaustive. As the series goes on it leaves out more and more, since simply appearing in the character list counts as a spoiler for some events.
Colleen McCullough's Masters of Rome series of historical novels. For the uninitiated, the seven book series covers Ancient Rome from 110 BC to 27 BC and has dozens of major characters and hundreds of minor characters, covering as it does several generations.
McCullough has the exact opposite problem from Tolkien; Romans only used a limited number of names and used them over and over and over! Keeping track of which Caecilius Metellus or which Appius Claudius is which is quite a challenge.
The number of significant characters in any specific Christopher Moore book is relatively small but since they're all loosely connected it adds up to a universal cast of scores.
The character lists in front of Larry Niven and Jerry Pournelle's jointly written works aren't absolutely mandatory, but they sure help keep everyone straight.
One Hundred Years of Solitude covers the story of a family, and by extension, an entire town, over the course of one hundred years of relative isolation. Naturally this means loads and loads and loads of characters, many of which having the same name (as is customary with Latin American naming), to the point that most editions of the book include a family tree at the start so readers can keep track of who they're reading about and who is related to whom.
The Tortall Universe has a new cast with each series, and characters from previous series often reappear in secondary roles. Executive Meddling about length slackened off considerably halfway through the Protector of the Small books, and every book since Squire has had a cast list at the end of it.
Psy Changeling features different main characters in each book, for more than a dozen books. It isn't particularly shy on adding side characters, either.
Thomas Pynchon's tomes are notorious for this. His masterpiece, Gravity's Rainbow, has over 400 named characters spread over 750 pages. Even more confusing, characters can disappear, or even die, early in the book, only to resurface at the very end as a key plot element.
The Rainbow Magic series has over 150 fairies and counting, with more being added every year.
Melanie Rawn is famous for this trope. At the start of the last book in her Dragon Star series she lists off some 50 different named characters who have died in the previous two books. Then she lists off some 75 "major" characters who managed to survive. She leaves some people off.
The prior trilogy, Dragon Prince has many of the same characters as Dragon Star. It doesn't have its own index at the back, but is rather in need of one.
Red Rising. Despite being a series where Anyone Can Die, there are several dozen significant characters to keep track of. Thankfully, with the different factions and caste-based society, it's fairly easy to organize characters according to Cast Herd. Even then it's hard to keep track because there are 14 castes, with characters from each spread across at least 5 different factions.
Almost every Redwall book introduces dozens of new characters. Luckily, most of them don't stick around for longer than one book.
Perry Rhodan. Running for over fifty years, covering a time line of over a million years and several different universes, the number of characters is correspondingly huge.
To put a number to this: the far from complete Perry Rhodan Wiki Perrypedia has over 9000note no, really (13.937 in the moment 2013) entries in the persons category.
Philip José Farmer's Riverworld series has so many named characters that take an active part in the story that you have to read the books with a cast roster next to you. By the end of the last book, there are over twenty characters (most of them real-life historical figures) to keep track of.
The Chinese epic Romance of the Three Kingdoms is infamous for having too many characters to count; the most recent video game based off the book and using the name (Romance of the Three Kingdoms XI) had about 700 playable characters, as there are many characters who appear very briefly or are only mentioned once; about 100 of these recur frequently. The Dynasty Warriors series had around 47 characters playable in the same game at one point, though.
Emile Zola's Les Rougon-Macquart is similar (not too surprising since Zola was influenced by Balzac), with over another couple of thousand characters, the vast majority named. Of these a good hundred appear in more than one novel and the members of the titular family that show up come up to 30 or 40. Made even more confusing by a strong case of Chekhov's Gunman as most of the family members are briefly mentioned in passing thousands of pages before they show up as main characters.
Each Edward Rutherford book covers tells the stories of a few families over hundreds, if not thousands, of years in a given location. As they tend to be historical fiction and not fantasy, there's a large attrition rate.
Safehold has the cast expanding extremely rapidly. Even if it has currently only six books, the sheer Doorstopper-class length of them, scale of events and number of one-chapter POV's makes it huge. So huge, at the end of Like a Mighty Army the character list (1 sentence about each person!) takes 90-freakin-pages...
K.J Parker's The Scavenger Trilogy, with the saving grace of a clear focus on a moderate number of central characters.
Charlotte Brontë's Shirley has so many characters that it doesn't get around to introducing the title character until about a third of the way through.
James Clavell's Shogun, which frequently switches character viewpoints without warning as we get to know everyone involved in the real life Gambit Pileup going on in Japan in 1600.
The ever-growing cast of characters in Lisanne Norman's Sholan Alliance series
Sisterhood Series by Fern Michaels: Okay, let's see. The series starts off with Nikki Quinn, Kathryn Lucas, Isabelle Flanders, Alexis Thorne, Myra Rutledge, Barbara Rutledge (she was killed, but she became a ghost), Julia Webster, Yoko Akia, Charles Martin, and Jack Emery. Then Harry Wong, Mark Lane, Bert Navarro, Ted Robinson, Countess Anne "Annie" Ryland de Silva, and Maggie Spritzer come into the pictures. Then you have Judge Cornelia "Nellie" Easter, Elizabeth "Lizzie" Fox, Pearl Barnes, Cosmo Cricket, Elias Cummings, Paula Woodley, Karl Woodley, Joseph "Joe" Espinosa, Rena Gold, Martine Connor, Henry "Hank" Jellicoe, Little Fish, Stu Franklin, and Abner Tookus. So what we have here is... 30 characters! Let's not get started on all the one-shot characters in the series!
Roy Dotrice was awarded the Guinness World Record for the greatest number of characters voiced in an audio book (224) for the unabridged version of A Game of Thrones. Martin suspects that Dotrice has already broken that record with the recordings for later books in the series.
As of A Dance with Dragons, the relevant wiki has at least 1853 named character pages. There have only ("only") been 35 narrators, though.
The Star Wars cast isn't at all huge (in the original trilogy, Luke, Vader, Leia, Han, Chewie, Obi-Wan, Lando, Yoda, Palpatine, R2, and 3PO, with honorable mentions to Boba Fett, Tarkin, Piett, and Jabba). Now let's take a look at both of the franchise's Expanded Universes.
The new Star Wars Expanded Universe has only been going since 2014, but has already racked up dozens of new characters across its works. And this isn't even counting the various Legends characters that have been re-canonized.
Star Wars Legends takes it to ridiculous extents. Practically everyone shown in the films have A Day in the Limelight, and if they centre around established characters each work insists on adding more and more and more...
Even that "R2 Unit with a bad motivator" from the first movie wound up being a secret Jedi robot in a dubious-canon side story.
The X-Wing Series. Consider: One squadron is composed of twelve pilots, optimally. Each pilot has one astromech droid which potentially has its own quirks and personality. The squadron also has at least one named mechanic and one quartermaster, as well as at least two higher-ups outside of the squadron. Main characters also have love interests, friends, and enemies. When a pilot dies, he or she is replaced by a new pilot with a new astromech. There is more than one squadron.
The novel Death Star has a lot of characters. Fitting, considering that it's about the Death Star and the people working on it. It's very big.
Theodor Fontane's Der Stechlin easily tops sixty named characters, and that is not counting off-page characters, dead characters or real-life persons mentioned in anecdotes etc.
Robert McCammon's Swan Song has well over twenty, though most of them don't live long. By the end of the book, only three of those we saw at the beginning are still alive.
Tailchaser's Song has so many characters that it has a several page index at the back that names most of the characters and their roles.
The Tale of Genji has Loads And Loads Of Characters stretching over four generations. To add to the fun cultural shibboleths meant that the author, 10th c. Japanese noblewoman Murasaki Shikibu, didn't give any of her characters names but referred to them indirectly by an ever changing collection of titles, residences, etc. all of which were held by at least two characters over the span of the novel and probably more.
Fiona Patton's Tales of the Branion Realm series is extremely dense. The series is historical fantasy, emphasis on historical, and not only are there lots of characters, most of them have titles and family trees. The depicted society is patterned on medieval Britain, and there are a dozen different knightly and religious orders for the characters to be members of. All these orders have their own officers, priests and assorted hangers-on.
The Thin Red Line focuses on a couple dozen different characters within the same company.
Harry Turtledove tends to have a dozen or more viewpoint characters, most of whom hardly ever interact. The time spent between seeing each of them makes learning just the names of the main characters quite a challenge, never mind the supporting characters in each one's story.
In Breaking Dawn, the third sequel to Twilight, author Meyer seems to just throw names at the reader sometimes (particularly when twenty-some-odd never-before-seen or only tangentially mentioned vampires arrive with about a quarter of the book to go), and then expect them to remember who she's talking about when she starts listing names of characters watching something happen. There's so many new characters thrown in that she actually needs to include an index so the readers can keep them all straight.
The count of moderately important characters to date in the Village Tales novels peers to poachers to publicans; canons and constables is already well over 225 ... in but three books. All of them with page time.
In The Wandering Inn, a lot of characters get their own POV moments, making you feel that no character appears 2-demonsional that doesn't mean, though, that the main characters are being neglected.
Space Marine Battles, being as it is a chronicle of deeds of various Space Marine Chapters, has a different set of characters in every novel, roughly twenty per novel. If that doesn't sound bad, remember that, counting short stories, novellas and audiodramas, the series has already forty installments...
Warriors has a section at the beginning of each book that lists most of the characters as of the book's first few chapters. There are so many of them that the author will actually forget that she killed a character the book before and list them anyway. Two notable examples: Smokepaw, a ShadowClan apprentice whose death was a pretty big event in Dawn, somehow came back in the next book and has since become a warrior, and Heavystep, who has been around since the beginning and has "died" more than once. Most of these characters never even appear in the books and are added on a whim (and then disappear—anyone remember Splashpaw? Robinwing? Oatwhisker), but, still.
The Allegiances sections in the later books list over one hundred characters.
There are also the characters who make it into the books but aren't in the Allegiances, most notably Rosetail from the first book who died attempting to protect the kits from ShadowClan but is never listed among the Thunder Clan elders.
Sign of the Moon has 147 characters in the allegiances. But PrequelSuper Editions are the worst offender, because all characters listed in the allegiences appear, and there and many characters born in them (Bluestar's Prophecy tried to explain the backstories of around fifty characters, while adding in fifty random new ones for good measure).
As of Hawkwing's Journey, the series has 1178 named characters, and several unnamed ones. Admittedly, most of these characters are just there to fill the allegiances, but it's still something.
Water Margin, which Suikoden is very loosely based on, has 108 'heroes'. The term 'heroes' is used VERY loosely here.
The Wheel of Time series is the absolute king of this trope. The total number of named characters was 2782. The original trio of Main Characters introduced in the first book—Rand al'Thor, Matrim Cauthon and Perrin Aybara—were last in one location in the fourth book, and never once reunited as a threesome again, though each pair had at least one moment in the final book. Only the Really Main Character, Rand, and the most prominent supporting character, Egwene al'Vere, manage to appear in all 14 books. All four characters have each acquired love interests (three in Rand's case), personal armies, and their own Cast Herds of supporting characters. The Big Bad has thirteen mini-bosses in the Forsaken, as well as numerous lesser Darkfriends. And almost every faction adds dozens of identifiable characters to the mix, sometimes with distinct subfactions within that which might as well be separate groups. And all these characters intermingle in an absolutely dizzying array of interactions.
Wild Cards, being written, amongst other people, by George R.R. Martin of A Song of Ice and Fire's fame, manages to keep a rather spectacular character tally, with each book having at least ten main characters with a huge amount of secondary and recurring secondary characters, amongst with a rather spectacular mortality rate.
Tad Williams tends to write lots of characters into his epic novels. Memory, Sorrow and Thorn features at least a dozen main characters and dozens of others scattered throughout the numerous subplots. It doesn't help that they are all off doing separate things at nearly every point.
Following in its wake, Otherland ups the ante by having a council of villains, a half-dozen hackers, a cabal of religious zealots, a Buddy Cop Show subplot, various minor protagonists, and more all trailing along in the wake of the heroes, who number at least a dozen all by themselves, depending on how you count.
Wings of Fire consists of several books with dozens of major characters. The first series has five main characters and various other major and minor characters.
Polish writer Joanna Chmielewska's second novel (Wszyscy jestesmy podejrzani) includes 25 murder suspects, all referred to by first names and with little defining characteristics. Remembering who is who can be complicated, even with the character list in the beginning. Same thing applies to several other of her novels.
Piers Anthony's Xanth series tries to keep track of every character in every book of the series, to the point that later books are merely the new characters making a tour of the place and meeting every other old character to see how they're doing. Most of the new characters always seem to be offspring of the old ones.