Sometimes one set of illustrations for a book or series, especially a classic, becomes so ubiquitous that those images become our cultural idea of what the scene or character "looks like," regardless of how it's described in the text.
There are three ways this can work. First, the illustrations may accurately follow the text. (This is generally the case when these illustrations have been vetted by the authors themselves.) Second, the illustrations may include prominent details that don't contradict the text, but also aren't mentioned. Third, the illustrations may outright contradict the textual descriptions.
Examples of illustrations that don't contradict the text:
- John R. Neill's illustrations for the early Land of Oz books.
- Sir John Tenniel's illustrations for Lewis Carroll's works, particularly the Alice in Wonderland books. It's worth noting that Carroll himself said he imagined Alice as a brunette, as Alice Liddell was (although her hair color is never mentioned in the text itself), but thanks to Tenniel's classic illustrations, she is almost always blonde even in other illustrations and adaptations to other media.
- Antoine de Saint-Exupery's The Little Prince, (self-admittedly poorly) drawn by the author himself. Re-illustrated versions are heresy.
- Garth Williams's illustrations of Little House on the Prairie, Charlotte's Web and other children's books.
- The Polar Express is famous for its gorgeous, full-page illustrations, most of which were reproduced in The Film of the Book (it was probably the point of making a movie to begin with).
- Paul Kidby's The Pratchett Portfolio, and subsequent Discworld covers.
- Any other illustrations for Dr. Seuss' books other than his own are practically criminal. All movies adaptations today are expected to resemble at least MOST of his drawings.
- The Zamonia books by Walter Moers (such as The 13 ½ Lives of Captain Bluebear, Rumo & His Miraculous Adventures, The City of Dreaming Books and The Alchemaster's Apprentice) all come with the author's own lavish illustrations.
- Munro Leaf supposedly wrote The Story of Ferdinand to offer his friend, the illustrator Robert Lawson, an opportunity to show his talent, and the book accordingly has always been published with the Lawson illustrations.
- Pettson and Findus is illustrated by the author himself.
- Fear and Loathing in Las Vegas includes the iconic and crazed cartoon illustrations of Ralph Steadman. The film adaptation includes a Steadman-drawn Mickey Mouse on the hitchhiker's shirt.
- Pan Tadeusz is inseparably associated with the illustrations by Michał Elwiro Andriolli from the 1882 edition.
- A Series of Unfortunate Events is illustrated by Brett Helquist in a very distinctive style which has become strongly associated with the books and the appearance of the characters.
- The Lord of the Rings had this before the films did, with the illustrations by John Howe and Alan Lee being the most prevalent visual depiction of the story. Peter Jackson brought both of them on as concept artists for these and The Hobbit trilogy, and such was their influence that some designs were put in unaltered and illustrations recreated as actual shots.
- Monday Begins on Saturday was illustrated in 1965 (and later re-illustrated in 1979) by Evgeny Migunov, and his work is considered the definitive portrayal of the books' characters and events in the former Soviet Union.
- The Good Soldier vejk: vejk's appearance is not described in the text but Josef Lada's illustrations are a staple of most editions of the book. Most people imagine him as a rather fat man with a very round and perpetually smiling face.
- When a 30th anniversary edition of Scary Stories to Tell in the Dark was released with new illustrations by Brett Helquist, it was not well received by longtime fans of the books. Helquist's illustrations were okay, but they just weren't Stephen Gammmel's. As one article comparing the two pointed out, it was the original illustrations, not the text, that terrified children and stayed with them long after they'd grown up.
- The Disney animated version of Winnie the Pooh has taken over from the Ernest Shepard illustrations as the "official" look for the characters, but recently, the Shepard "look" has gained a resurgence as the "classic" look for Pooh.
Examples of illustrations that include important details not mentioned in the text:
- Sherlock Holmes and his deerstalker hat, added by Strand artist Sidney Paget (but only when Holmes was in the countryside).
- In the Magic School Bus books, the text and illustrations complement each other, with the illustrations and dialogue frequently including details the text leaves out. For example, the text of most of the books doesn't mention any of the children's names, but they are all worked into the dialogue.
- Going back to Tenniel and Alice in Wonderland, the price tag on the Mad Hatter's hat ("In This Style 10/6", the fraction being ten shillings and sixpence in the old monetary system) was Tenniel's own invention and nowhere to be found on the text. It has been retained in some form or another in almost all adaptations.
- It was also apparently Tenniel's choice to draw the Lion and the Unicorn in Through the Looking-Glass as caricatures of Gladstone and Disraeli.
- Snape is never described as having a beard in Harry Potter, but the goatee Mary Grandpre gave him became Fanon. However, it's been largely superseded by Alan Rickman's portrayal of him in the movies.
- Before the films, a lot of Harry Potter merchandise seemed to copy the look of Mary Grandpre's illustrations, including kind-of-sort-of keeping her "soft geometry" art style.
- Paul Kidby's illustrations to The Last Hero, adding such details as Ponder's "Actually I Am A Rocket Wizard" Fun T-Shirt, now as ubiquitous to the character as the robe that looks like an old-fashioned anorak (which is in the text). Defictionalisation has occurred.
- Rudyard Kipling's illustrations to the Just So Stories - which are left out entirely or replaced with new ones in many editions - contain quite a bit of additional information in the accompanying explanations, for instance the names of some characters that are not named in-story (e. g. the Rhinoceros and the Parsee are called Strorks and Pestonjee Bomonjee, respectively) or what happened afterwards (e. g. the Whale and the little 'Stute Fish became good friends again after the Whale got over his temper). One of the illustrations of The Coming of the Armadilloes tells an entirely unconnected story of an expedition to the mouths of the Amazon in the 16th or 17th century.
Examples of illustrations that contradict the text (for instances of lying book covers, see Covers Always Lie):
- Heidi is described as having short, black, curly hair. She's drawn as a blonde.
- The original illustrations from Conan the Barbarian's magazine serialization depict him as the now-stereotypical Loincloth-clad brute, but in the actual text what Conan felt to be one of the advantages of his stature was the ability to wear very heavy armor (usually chainmail over leather) while remaining agile and unencumbered. Conan generally wore whatever attire was appropriate for the climate and culture he was in at the moment, so there were a few instances where he actually did wear a loincloth, but certainly not as much as the illustrations would have you believe.
- The Dark Tower books...in some of them, Jake is described as having blonde hair, but in one illustration has black hair.
- The Pauline Baynes illustrations of The Chronicles of Narnia. She contradicted Lucy's Hair of Gold, Heart of Gold, but people still believed in her chosen colors for the rest of the (never-described) kids enough to complain about the Adaptation Dye-Job when the recent movies gave Peter blond hair and Edmund brown/black hair, the reverse of how she drew them.
- Ciaphas Cain is always depicted in illustrations carrying a Bolt Pistol, despite using a Laspistol in the books. This is apparently deliberate, to reflect the fact that the images are meant to be ridiculously over-the-top propaganda posters. One later book does mention that he has a Bolt Pistol to brandish dramatically for portrait sittings and photo ops, but he still almost always uses his trusty Laspistol in actual combat (he sometimes has the chance to take something bigger, but always keeps the laspistol due to being a better shot with it. Considering he's taken out purestrain genestealers and ork warlords with the weakest standard weapon in the setting, you kind of see his point).
- Tomcat Blue Eyes' Diaries: Blue Eyes and Kiki are both explicitly identified as Siamese cats so they should be silvery or white with various forms of darker point colouration. Helena Zmatlíková's illustrations depict them as blue-grey cats, similar to Russian Blue or British Shorthair Blue, albeit with blue almond-shaped eyes. The charming illustrations are included in all editions of the book and all covers of audio books so most people imagine Blue Eyes and Kiki as grey kittens.