Click to viewAlien zoo sex, vulgar language, and the horrors of war have earned this novel (which shall remain nameless) a place on many a banned books list. And it's hardly alone. Even in just the last decade, parents have tried to remove their least favorite titles from school libraries, and works of science fiction have been among the casualties. So, grab a flashlight, hide under a sheet, and read (or re-read) science fiction's most suppressed books of the 21st century.These books come from the American Library Association's most frequently challenged books from 2000-2007:

Captain Underpants and The Adventures of Super Diaper Baby by Dav Pilkey Position on the List: #10, #47 Why it gets Challenged: Ever since Dav Pilkey released his series about alien-empowered underage superheroes, they've topped the banned books list. Parents have complained about the language (which includes such linguistic horrors as "Poopypants" and "Booger Boy") and that the protagonists routinely defy their nasty principal. Most parents, though, are just happy their kids are reading.

The Giver by Lois Lowry Position on the List: #21 Why it gets Challenged: As frequently happens with challenged books, parents who complain about The Giver tend to miss the point. They cite features of Lowry's initially appealing but ultimately dystopian society in their complaints, namely the low social status of biological mothers and the practice of infanticide and euthanasia. Then again, some just don't like that main character Jonas feels "stirrings" when he sees a pretty girl.

His Dark Materials by Philip Pullman Position on the List: #29 Why it gets Challenged: Predictably, Pullman's interdimensional saga is frequently challenged for its portrayal of the Church and figures from Judeo-Christian tradition. Pullman, for his part, says that every banning of his books fills him with glee, since it tends to result in higher sales.

Brave New World by Aldous Huxley Position on the List: #37 Why it gets Challenged: In another instance of colossal misreading (or failure to read), Huxley's work, one of the most banned of last century as well, gets challenged because the soulless, pill-popping world Huxley meant to criticize is such a downer.

Slaughterhouse Five by Kurt Vonnegut Position on the List: #45 Why it gets Challenged: Violence? Check. Blasphemy? Strong language? Magic Fingers? Check. Not only has Slaughterhouse Five been challenged in school districts, just last year law enforcement in Howell, Michigan was asked to review the book to determine if any of its contents were illegal.

Fahrenheit 451 by Ray Bradbury Position on the List: #72 Why it gets Challenged: Perhaps missing the humor in attempting to censor a book on censorship, challengers still go after Fahrenheit 451 because its firemen characters smoke, drink, and swear. And at least one complainant claimed its discussion of the Bible offended their religion.

Shade's Children by Garth Nix Position on the List: #85 Why it gets Challenged: That the titular children of Nix's dystopic young adult novel grow up fast leaves a lot of parents anxious. Vulgar language and a post-apocalyptic key party keep it on the ban list. Top 100 challenged books of 2000-2007 [American Library Association]