How It All Goes Down
First things first: this book is made up of several smaller books. To keep us all on the same page, check out how we cite them throughout the guide.
S=The Sword in the Stone (short title = Sword)
Q=The Queen of Air and Darkness (short title = Queen)
K=The Ill-Made Knight (short title = Knight)
C=The Candle in the Wind (short title = Candle)
Got it? Good. Moving on then…
The Sword in the Stone
Meet Wart. He lives in a fancy castle with his foster father, Sir Ector, and his foster bro (fro?) Sir Kay. When Wart grows up, he's going to be Kay's squire. Merlyn, a mystical, magical mister who lives backwards through Time (so can predict the future—sometimes) answers an advertisement to be tutor for the two.
And what an education he gives Wart. He turns the young boy into different types of animals, such as a falcon, an ant, a goose, and a badger—all to teach him lessons about the world. Mostly about power, force, and tyranny. He learns that Might does not make Right.
In the meantime, King Uther Pendragon has died without leaving an heir to throne—never a smart thing to do—and a mysterious stone appears in a churchyard in London. It has an anvil on top of it, with a sword stuck in it. Rumor has it that whoever can draw the sword from this stone (or anvil, actually) will be the true, legit king of England. And hey—what a coincidence. Sir Ector, Kay and Wart just happen to be in town right at this time for Kay's very first tournament (he's just been made a knight).
On his big day, though, forgetful Kay leaves his sword behind at the inn, and sends his trusty squire Wart to go find a replacement. Too bad all Wart can find is the old crummy sword stuck in the stone. Oh well; it'll have to do.
Wart draws the sword and takes it to Kay, who initially tries to take credit for it, but then admits Wart is the one. Suddenly, Wart is now King Arthur. Huzzah!
The Queen of Air and Darkness
The Orkney boys (Gawaine, Agravaine, Gaheris, and Gareth) are living a hard life in the cold and harsh climes of Scotland. Their mother, Queen Morgause, doesn't really give a fig for them, and is too wrapped up in her own pursuits, which include witchcraft and men.
Meanwhile, King Arthur is trying to get his kingdom whipped into shape, and is about to engage in a battle to rein in King Lot and the eleven kings that are siding with him against Arthur. Did we mention King Lot is Morgause's husband?
Merlyn instructs Arthur in some rather underhanded battle tactics (such as a night ambush) to defeat Lot and his guys faster—and to save the lives of the poor, unarmed cannon fodder (also known as serfs or peasants) that are the real ones who suffer anytime two or more powerful medieval factions want to whack each other.
In short order Arthur defeats Lot and sends him back to Orkney with his tail between his legs. Queen Morgause wants to kiss up to the new ruler, so she packs up her four wild sons and heads Arthur-ward. Seriously: she literally wants to kiss/up to Arthur, and uses a magic item called a Spancel (which is a piece of tape made from a dead human skin, yum) to seduce him.
What Arthur does not know (and Merlyn knew he was forgetting to tell him something important) is that Morgause is actually his sister. So, yeah: incest. Nine months later, Mordred is born. This sin is what causes Arthur to have a tragic ending.
The Ill-Made Knight
Arthur is now married to Guenever, and has created the Round Table, an organization of knights who are supposed to stand for Truth, Justice, and the Arthurian Way. Fighting bad guys and rescuing damsels in distress is Arthur's idea of how to channel aggressive impulses into serving the good.
Lancelot is an ugly knight who worships Arthur and whose major life goal is to perform just one true miracle at some point. He also ends up falling in love with Guenever. The two start an affair that lasts many years. In between their periods of happiness, Lancelot rescues a maiden from boiling water (it's a miracle!), gets her pregnant (the offspring is Galahad, who eventually nabs the Holy Grail), and goes crazy, turning into a Wild Man who runs naked through the forest because Guenever tells him to get lost.
Meanwhile, there's a whole lotta feudin' going on, with the Orkney family battling it out with the Pellinores because King Pellinore accidentally killed King Lot. So, things spiral out of control and end with Agravaine killing Queen Morgause because she was bedding down with Sir Lamorak (Pellinore's son). Then, Gawaine, Agravaine, and Mordred murder Sir Lamorak in an unfair (and unknightly) fight of three against one.
Arthur starts to realize that it's not enough to channel aggression into worldly good, so maybe channeling it into spiritual good will do the trick. He calls for his knights to go on a quest for the Holy Grail. This doesn't turn out so great, since most of his knights can't really stop themselves from going for the sword, or women, or the drink. Out of 150 knights, only three are worthy enough to achieve the Grail: Sir Galahad (who is too inhumanly perfect), Sir Percivale (who is a complete innocent), and Sir Bors (who is a born-again virgin who hates women).
The Grail Quest ends up being a sort of mixed bag as far as success goes. Sure: the three perfect knights get to see the Grail (and two of them go bye-bye to Heaven, presumably, because they're too good for this world). But many of Arthur's knights have died on the quest. Plus, once Arthur's leftover guys return to court they now have nothing to do other than return to their sniping, feuding ways.
Guenever is accused of trying to murder Gawaine with poison, and is almost burned at the stake, but Lancelot comes riding to her rescue. Then, a low-class knight, Sir Meliagrance, kidnaps Guenever, but (wait for it) Lancelot comes riding to her rescue. He tarnishes his Captain America good-guy image quite a bit, though, when he for all intents and purposes murders Meliagrance to shut him up about Guenever's unfaithfulness.
Shortly after this, a Hungarian knight named Sir Urre comes to court needing to be healed by the Best Knight of the World. He's got festering wounds that won't stop bleeding (like something out of The Walking Dead), but Lancelot is able to heal him. Barely.
The Candle in the Wind
It's many years later, and all of the major players here are old—at least middle-aged. Arthur is an old, old man, and Guenever and Lancelot have both gone gray, but they still love each other.
Mordred and Agravaine are plotting to get Arthur and Lancelot out of the picture: Mordred hates Arthur because when he was a baby, Arthur tried to get rid of him (and the evidence of the incest with his sister) by ordering all babies born on a certain date to be floated out into the ocean on a rickety raft. Agravaine is just jealous of Lancelot, and wants him out of the picture.
The two evil brothers tell Arthur that Lancelot and Guenever have been having an affair (gee, guys, why don't you tell him something he doesn't know?), and this forces Arthur to act. They set up an ambush to catch Lancelot in the Queen's room, and during the scuffle Lancelot kills all twelve knights (except Mordred, who runs like a little baby). Guenever is to be burned at the stake for treason, but… Lancelot comes riding to her rescue.
Everything could be patched up at this point, but Lancelot makes one crucial mistake: he accidentally kills Gareth and Gaheris, who are unarmed in the battle. So Gawaine convinces Arthur to go to war with Lancelot instead of making up with him and going back to being besties.
While Arthur is off in France trying to defeat Lancelot (well, pretending to try, anyway), Mordred tries to take over in England, even forcing Guenever to marry him. She locks herself up in the Tower of London and Arthur returns, engaging in battle with his son/nephew. Lancelot comes riding to the rescue, but before we see the final battle, Arthur decides that the circle has to be broken, so he tells his entire story to little Tom the page (a.k.a. Thomas Malory), who will write everything down and preserve Arthur's ideals for the future. Then Arthur either dies or is carried off to the magical island of Avilion, from where some say he'll eventually come back in better times.