see this previous post), and one of the most interesting authors writing for that audience is David Levithan. He has collaborated to write such popular YA titles as Nick and Norah's Infinite Playlist and Will Grayson, Will Grayson. He has written plenty of books on his own as well, including Boy Meets Boy, one of the first YA books to feature gay characters where their struggle with sexuality didn't provide the main narrative arc. Levithan is not afraid to play with narrative forms his "Lover's Dictionary" reveals the story of a relationship through encyclopedia-like entries for each letter of the alphabet.
And his most recent book, Every Day, might just be the most thought provoking love story on the shelves. It tells the story of "A" - a being who finds itself in a new body each day, consistant only in age and relative geographical proximity, A is aware of the hosts memories but not emotions and has grown up with this changeable existence developing the insight of an outsider to the usual flow of human life. And one day "A" meets a girl. Levithan navigates this tricky premise well and while he sometimes gets a little too direct about his message that our selves are not defined by our bodies, he pulls off a believable, generous love story and makes the crazy circumstances fade into the background of the developing characters. Levithan is better at gender, sexuality and mental illness than he is at race and class. Major points however for the best depiction of a transgender character I've read yet.
Funny, touching, thought-provoking. Put Every Day on your to-read list.