Books with an abrupt and bewildering change of tone (spoilers)

Let’s think of some books where the author has you expecting one kind of story all along and then suddenly everything changes with no apology. My examples are modern pop fiction but I’m sure people will be able to come up with some that are classics.

Nuklear Age was [del]probably[/del] definitely the worst book I have ever read. It’s a parody of a superhero story, where the hero thinks he’s great but is actually an idiot, and the sidekick is desperate for some kind of validation that he’s actually smarter. They pick up stock character friends along the way. Then, all of a sudden, in the end of the book, disaster strikes, the hero dies, and everyone is left miserable, while the author flails about trying to be profound.

Special Topics in Calamity Physics, which I actually liked, is about a young bookish girl whose father is a professor and has moved the two of them around to various small towns in the United States. Finally, dad agrees that the two of them will settle down for one full year, the girl’s senior year of high school. We are told from the beginning that her life was dramatically changed by the death of a woman named Hannah. The girl attends a fancy prep school and is drawn into the exclusive circle of four rich kids and Hannah, one of the teachers. This looks like it’s going to be a coming-of-age story about friendship and family and coping with death, and then we discover that Hannah’s death was a conspiracy by a massive secret organization in which Dad was himself involved, and the last few chapters are dedicated to the history of the organization and its role in Hannah’s death.

While I did like Special Topics, I could see how some readers would be turned away in disgust just as I was from Nuklear Age. What are some other examples of books where the entire genre changes in the ending?

Kate Elliott’s Jaran books:

[spoiler]There’s only 4 books out of 9 completed, but book 1 starts off as kind of historical fantasy, except instead of like typical medieval stuff the main characters are tribal Russian nomads. We’re vaguely aware that the main character is actually from Earth in the future and the planet she’s on now has been set as a protected zone where scientists can watch actual evolution take place which is why they are so technologically behind.

Anyway, so the sci-fi element is barely noticeable in the first book and just seems like a plot device to make the two protagonists very different.

The next books delve further and further into the sci-fi aspect until you realize you’re no longer reading an historical fantasy novel but a sci-fi novel in which the original characters are all just pawns in the larger galaxy.
[/spoiler]

Alfred Bester’s The Computer Connection. There is a point about 2/3rd of the way where the book turns from a first-class SF thriller novel to really crappy and dull. It’s as though he just lost interest at that point.

Not a single book, but a trilogy. In the Gormenghast trilogy by Mervyn Peake, the first two novels, Titus Groan and Gormenghast are set in an immense, isolated, gothic castle. The third volume, Titus Alone, is drastically different in tone and setting, as Titus leaves the castle to travel to a modernistic city.

Dexter in the Dark, the third book in the Dexter series. Turns out Dexter isn’t a serial killer because of the trauma he witnessed as a child, but because

[spoiler]he is possessed by a several-thousand years old demon. Seriously. The demon is an offspring of the evil god Moloch, who’s been around since the beginning of time. The demons can leave their human hosts, jump from body to body and communicate with each other.

Seriously.[/spoiler]

The Once and Future King. The first part, “The Sword in the Stone”, is full of light-hearted humor. Then it shifts into a sort of dark psychodrama. (It should be noted that this is actually a conglomeration of works that were written separately.)

Yes, I stopped reading Dexter after that. What a stupid arch to take the plot on. I was so very disappointed with the author after that one - how can he expect us to take him seriously now?

The Difference Engine, the steampunk SF novel by William Gibson and Bruce Stirling, just dissolves into disconnected notes and fragments for the last third of the book.

Bee Season by Myla Goldberg – starts out as a quirky story about a girl determined to win the National spelling bee, and hangs a weird left turn into Kaballah halfway through and the spelling bee thing just fizzles out.