We divide fiction into genres. Usually you can tell from a glance at the cover whether it's General Fiction or Crime or Science Fiction or Fantasy or Romance or whatnot. And we all discriminate.
The Science Fiction Ghetto is well-known enough that it's got its own page at TV Tropes. Some well-known authors, fearful of being shunted from Serious Literature to Science Fiction, will deny writing SF even while quite blatantly doing so. (Margaret Atwood's probably the most infamous example of this). But Iain Banks quite cheerfully and profitably writes both SF and mainstream fiction, so it's obviously possible for an author to live a cross-genre existence without compromise.
And we all discriminate. I discriminate. I never pick up novels specifically marketed as Romance or Erotica, even though I have no aversion to romance or sex in my reading. I'm not greatly interested in the genres of Military Fiction, Mystery or Crime, although I'll make exceptions for certain authors (like Carl Hiaasen) and for books I've heard are good. And I have a complex algorithm for determining what science fiction I'll sample. I don't like media tie-ins, I don't like overly long series, and I'm not terribly fond of "space opera"-type SF, although any and all of this can be disregarded if I hear a book seriously, totally kicks ass.
And then there's Young Adult. I pay so little attention to YA that I don't even have an opinion on it. It's just a big blind spot.
Maybe that needs to change.
I'm midway through Markus Zusak's The Book Thief. I picked it up in a used bookstore (to be more honest, my fiance did) and brought it home. I'd never heard of the author or the title, even though the cover proclaims it "The Extraordinary New York Times #1 Bestseller" and is covered with praise from critics and various accolades the book has received. Why hadn't I heard of it? Well, it's YA, and YA goes under my radar. Or over it. Or something.
It's set in Nazi Germany. It's the story of a young girl who lives with foster parents in Bavaria, who finds herself sheltering a Jewish man in her basement. The novel is narrated in the first person by Death Personified.
Unless the quality of the writing somehow catastrophically plummets in the book's second half, The Book Thief is as good as any book for adults I've read in the past year.
Why is The Book Thief considered YA, instead of general fiction for adults? Because it's somehow juvenile?
Ha. Anyone who thinks YA = juvenile needs to read The Book Thief and then write "I will not call YA novels juvenile" on a blackboard one hundred times.
Because it's written in a style that often gets playful, with the narrator addressing the readers directly, which some might feel is reminiscent of children's books?
But there have been plenty of accoladed novels in the past decade that do that; Yann Martel's Life of Pi and Zadie Smith's White Teeth are two well-known examples I've read.
Because the protagonist is a teenage girl? But plenty of general-fiction novels have young protagonists.
If The Book Thief were published as general fiction, no one would ever think of saying "But this is clearly YA! It's a kid's book!"
The Book Thief is YA because it was published as YA. No other reason. Oh, I'm sure Markus Zusak wrote it with the YA market in mind, so the book probably reflects that. But I only get to see the finished product, not the writing process that produced it, and I say this is a book that could have easily been published as general fiction without raising any eyebrows.
So am I saying that the book was somehow done a disservice by being marketed as YA? No. No no no. Then I'd be no better than people who say "Book X isn't science fiction because science fiction is CRAP but Book X is GOOD!"
The Book Thief is totally suitable for readers in the 12-15 age range. Yes, it's dark and disturbing. So's the world.
It's also suitable for ages 16 and up. I'm 29, and I think I can handle it.
Tor.com's got a smart post up about YA by author Mary Pearson. Highly recommended.