This post isn't related to Asperger's Syndrome per se, but I think people with AS are more likely to identify with it.
Children's fiction is imaginative. The sky's the limit. Dinosaurs talk. Kids have super powers or can cast spells. Monsters are friends with children. And so forth. The scope of fiction narrows as you head into the intermediate and young adult section of bookstores and libraries. You won't see talking dinosaurs or friendly monsters, but a lot of imagination is still there, even in popular fiction. Harry Potter, need I say more? I actually really enjoy teen fiction. Even when a large focus of the story is centered on "high school drama," I've found that characters often have unique voices. Additionally, lots of teen fiction deals with issues such as challenging authority and "coming out of the closet." Sometimes these themes are presented in unique ways, such as in The Hunger Games.
Now walk into the adult section. Maybe I'm not looking hard enough or in the right places, but imagination seems mostly gone. So much adult fiction seems to be midlife drama, and very little of it has any kind of unique twist. As I stated, even "high school drama" books have a level of creativity. But seriously, it is so difficult to find an adult book that isn't about some woman having a mid-life crisis, or a man having an affair, or a woman feeling like dirt because she can't pop a baby out. Even in books advertised with unique storylines, these storylines take a backseat to mid-life drama. I am almost finished reading Mercy by Jodi Picoult. The book is allegedly about a mercy killing. However, the majority of it is about a man having an affair with another woman. False advertising! About 3/4 of this book would have to be cut if it were to be entirely about a mercy killing. If I read one more time about how Cam "pulls out of Mia at the last minute," and "spills," I'll mercy kill myself!
For this reason, I stick to YA fiction and the adult books I read are largely non-fiction.
To me, this progression of children's fiction to adult fiction represents the evolution of the neurotypical human mind. Children are largely imaginative. In the teenage years, some imagination is lost in favor of romantic relationships, but relationships are only one part of life. In adults, it's all about marriage and procreating. I know I'm making a generalization here, but that's how it seems, and fiction seems to represent this. We Aspies get tired of everything being about romance. We want books that make us think and that have a unique story from a unique perspective. Alas, publishers obviously realize that unless a story has at least a subplot with a romance in it, it won't sell. Adult fiction often has to be Adult fiction to sell.