Second-Hand Storytelling: Explained by Word Of God that the story is mostly seen from a hobbit POV, since it was hobbits that wrote the tome professor Tolkien translated. Example events include Gandalf's imprisonment by and escape from Saruman, The Ents' attack on Isengard, Aragorn's adventures in southern Gondor. Also note that parts of the story with Aragorn, Legolas and Gimli traveling away from the rest of the Fellowship (the majority of The Two Towers and the Paths of the Dead) are known to the Hobbits because they shared their stories with them at Isengard and Minas Tirith respectively.
Secondary Character Title: The Lord of the Rings refers to Sauron not Frodo as some believe. The full title of Frodo's book about the war is The Downfall of the Lord of the Rings and the Return of the King.
It is a particularly strange error to ascribe such a title to Frodo, as there is a scene where Pippin says, "Make way for Frodo, Lord of the Ring" and is quite strongly corrected about it by Gandalf.
Shout Out: There are several to Macbeth, all taken from Act IV, Scene i, when the Witches tell Macbeth their prophecies of his death. First of all, the phrase "Crack of Doom" was coined by Shakespeare in this scene. The Ents' besiegement of Isengard and the Witch-King's defeat by Éowyn are references to two of the three prophecies—namely, that it will not happen until "Great Birnam Wood...shall come against him" and that "none of woman born shall harm" him. Of course, the trees do come to the castle when Macduff's army uses their branches as camoflauge, just as the Ents come to Isengard, and Macbeth is killed by a man who was not born, but removed from his mother's womb, just as the Witch-King, who can be killed by "no living man," is killed by a woman.
To "Arabian Nights", oddly enough. Compare this tale and the chapter "The Voice of Saruman" and try to find the differences.
Shown Their Work: Tolkien's understanding of Mythology, Linguistics, Geography, Geology and Climatology are masterful.
Shrug of God: Tom Bombadil. In response to a question from a fan about his true nature:
"Even in a mythical Age there must be some enigmas, as there always are. Tom Bombadil is one (intentionally)."
Signature Item Clue: Peregrin Took drops his elven brooch while being transported by his orcish captors, in hopes his friends will pick up his trail. The gambit pays off.
Simultaneous Arcs: The main continuity splits off into two branches when the Fellowship breaks up near Rauros - one arc following Frodo, Sam and Gollum in the journey to Mordor, the other one following everyone else and the wars in Rohan and Gondor. The second arc itself splits, rejoins (at Isengard), and then splits into three (with Pippin and Gandalf to Minas Tirith, with Merry and the Rohirrim, with Aragorn, Legolas, and Gimli through the Paths of the Dead).
Further subverted in that although the Gondorian and Arnorian branches claim direct descent from Elros, first king of Númenor, they are not descendants of the last king, as their ancestor branched off from the eldest daughter of the 4th king. Also found All There in the Manual.
Sleep Cute: Gollum has a Pet the Dog moment when he catches Frodo and Sam doing this on the stairs of Cirith Ungol.
For a fleeting moment, could one of the sleepers have seen him, they would have thought that they beheld an old weary hobbit, shrunken by the years that had carried him far beyond his time, beyond friends and kin, and the fields and streams of youth, an old starved pitiable thing.
Sleeping Dummy: The hobbits pull this off at the Prancing Pony in Bree, with the help of Barliman the innkeeper.
Sliding Scale of Idealism Versus Cynicism: Heavily on the idealistic side. Evil may triumph temporarily, but in the long run it's made very clear that evil is nothing but a hollow mockery of good and is destined to lose in the end. That does not, of course, mean that in the immediate term Sauron is any less of a threat.
Well, sort of. Gandalf makes it clear that fighting evil is a constant thing, and that plenty of evils will come after Sauron is defeated.
Even then, however, the nature of Good and Evil in Middle-Earth is heavily influenced by Tolkien's Catholicism. Good and Evil are not equals, and while the latter may dominate for a time and seem unstoppable, when all is said and done the former is stronger.
Some essays point out that the combination of Earn Your Happy Ending, the general hopelessness of conventional victory, the Norse "Theory of Courage" one could equate to Knight in Sour Armor -ness at times, and the fact that Frodo is so physically and emotionally beaten by the Quest to the point that he can no longer continue to live on the Middle-Earth he saved makes this work, while still decidedly idealist, hardly a super-happy-Tastes Like Diabetes ending.
Someone should have explained that to Edmund Wilson. Or to Edwin Muir, who wrote that The Lord of the Rings was a painlessly "sub-adult" work filled with boys who "knew nothing of women", where "the good boys, having fought a deadly battle, emerge at the end of it well, triumphant and happy." Did he even bother to read the thing?
Staff of Authority: The Istari, including Saruman and Gandalf have staffs that seem to be symbolic as well as practical. In their confrontation at Isengard after the Ents march on the place, Gandalf breaks Saruman's staff to show that his authority has been revoked by the Powers That Be.
Stay on the Path: Averted. Gandalf tells the hobbits to stay off the roads on their way to Bree.
Stealth Pun: Merry is given the name "Holdwine" by Éowyn and Éomer once, and it's never mentioned again. It means "loyal friend" in Old English, but in Modern English ...
Steel Mill: Saruman runs one at the basement of Isengard. Instead of coke, he uses charcoal made from trees as the iron reducing agent. Which, of course, the Ents find less than amusing, considering the sheer number of trees he's cut down.
A Storm Is Coming: When Gandalf came bearing news of Saruman's plans to the Rohirrim. King Théoden (still under Saruman's influence by way of Wormtongue) calls him "Stormcrow", and Wormtongue mocks him: "Láthspell I name you, Ill-news; and ill news is an ill guest, they say."
Stranger in a Familiar Land: When they return home after the War and the Shire is back to normal after its occupation, all of the four hobbits do feel this effect to varying degrees. While the other three are coping with it, Frodo, with the additional burdens of the Ring and his other wounds, cannot "return home" or find peace again; he leaves the Shire to sail to the West with the Elves.
Succession Crisis: Gondor had a brutal civil war over who should inherit the throne, a half-breed or a pureblood. A generation later, when the last king of Gondor foolishly rode off toward captivity and (presumed) death, there was no one left willing to take the throne, for fear of a second civil war.
Sympathy for the Hero: Saruman expresses respect mixed with hatred for Frodo at the end of Scouring of the Shire.
Take Our Word for It: Gandalf's description of the "nameless things" that dwell beneath Moria; Tolkien's description of many of the Orc's family-unfriendly habits, and of Sauronhimself and his hideouts. If it's something of which Gandalf or Aragorn "will not speak... to darken the light of day", you know it's bad.
Aragorn seems to have encountered the Ringwraiths personally at least once before he met the hobbits in Bree; the only description he can bear to give is simply: "They are... terrible." And as he says it, his hands are clutching the arms of his chair so tightly that his knuckles turn white.
Take That, Critics!: In the Foreword: "Some who have read the book, or at any rate have reviewed it, have found it boring, absurd, or contemptible; and I have no cause to complain, since I have similar opinions of their works, or of the kind of works that they seem to enjoy."
Take Up My Sword: Isildur takes Narsil from his dead father, and 3000 years later Aragorn uses the same sword re-forged in the War of the Ring.
A literal, unspoken example when Sam, believing Frodo dead from Shelob's poison, takes Sting (and the Ring).
Tangled Family Tree: The Hobbits. Thanks to generations worth of intermarrying between the Tooks, Bagginses, Bolgers, and Brandybucks (all of them among the most respected families in the Shire), Frodo is Bilbo's first and second cousin, Pippin's second and third cousin, Merry's first, second, and third cousin, and his own third cousin! Sam, in fact, is the only major hobbit character who isn't related to any of the others - although once his children reach marriageable ages...
Think Nothing of It: Faramir has such a moment after Sam compliments him for rejecting the Ring.
‘Yes sir, and showed your quality: the very highest.’ Faramir smiled. ‘A pert servant, Master Samwise. But nay: the praise of the praiseworthy is above all rewards. Yet there was naught in this to praise. I had no lure or desire to do other than I have done.’
Together in Death: Arwen chose a mortal fate (much like her ancestor Lúthien in The Silmarillion) so that she could die soon after Aragorn and follow his spirit out of the world.
Translation Convention: All of our real-world languages do not exist in Middle-earth, and so the common Translation Convention applies. When not convention-translated, names and speech make use of either Tolkien's constructed languages, or of a real-world language used as stand-in for a fictional one. The latter ones are not chosen randomly, but to represent the relation between the respective 'proper' languages, or a certain image. Languages regularly replaced by stand-in languages in the text are: "Westron" aka the "Common Speech" is always rendered as English (as it is the Third-Age-novel's POV-character's language), the Rohirric language by Anglo-Saxon aka Old English (to appear vaguely familiar to the hobbits' Westron-English), and the language used by the Dwarves and the Men of Dale by Old Norse. Information on the 'translation' and what these languages 'really' look like, can be found in various appendices and additional texts.
If you read the appendices you also find out that the "original language" version actually has features which influence the plot, but which are not rendered in the English "translation". One of such is the contributing factor to the rumor in Minas Tirith that Pippin was a Prince of high status and power: hobbits no longer have/use a formal address, so Pippin's informal address to Denethor made the listeners think he would have to be of high status indeed. It's better implied in some of the foreign translations, in languages that do still have formal and informal variations of "you" (the hobbits simply don't use the formal ones).
Took a Level in Badass: The main hobbit characters start out as mild-mannered rustics, and by the end have become some of the greatest heroes of the Age.
There's a Bigger Bad in the Back Story. Then again, Tolkien states that Sauron at the height of his power was more powerful, in a sense, than Morgoth during the War of the Jewels, as Sauron merely strove for "superficial" domination: an empire on the earth and control of the wills of others, while Morgoth wanted to control the very matter of the universe. Interestingly enough, he's not motiveless Evil Incarnate: his Start of Darkness was motivated by a desire for order and control, not destruction.
Depending on which version you favor, Morgoth started out far more powerful than Sauron but graually became weaker as he spent his power damaging the world. (At the start of The Silmarillion the combined powers of all the other gods/archangels can barely hold him off; but towards the end of the War of the Jewels one single Elf challenges him to a duel and manages to wound him seven times.)
Undead: The Nazgûl and the Dead of Dunharrow. The barrow-wights however, are evil spirits possessing the remains in the barrows, so are functionally undead.note Word Of God suggests the spirits could be the ghosts of elves who rejected the authority of the Valar, and were instead enslaved by Sauron, making the barrow-wights fully undead, but there is room for doubt.
Unintentional Backup Plan: Gandalf and Aragorn's Batman-Gambit pays off in getting the One Ring to Mount Doom, but the One Ring itself spans their plans by finally corrupting Frodo at the last crucial moment. Fortunately, Gollum shows up to take the ring for himself before accidentally falling into the volcano and destroying it.
Unstoppable Rage: After seeing Éowyn apparently dead on the Pelennor fields, Éomer takes up the Battle Cry of "Death! Death!" and he and his men become an unassailable force of vengeance for the rest of the battle.
The Usual Adversaries - Orcs mainly, but the Dunlendings, Easterlings and Haradrim as well to a lesser extent.