Stonewall Book Award winner (for LGBT books) in the Children's and Young Adult category is Almost Perfect by Brian Katcher. It's an interesting and fairly realistic portrayal of the trials of being a teen transsexual, and I would certainly recommend it to everyone, not just LGBT-interested readers. The themes of acceptance, self-doubt, and societal pressures apply equally to anyone.
Katcher makes the book especially powerful for communicating to non-LGBT readers by structuring the book as a narrative, not by a transsexual girl, but by a boy who befriends a transsexual girl. His questioning of his sexuality (he is hetero), his sometimes painful 20/20 hindsight, and his viewpoints, are all convincingly real for a small-town teenager. As for handling of the transsexual character, there is a lot of explanation to fit into a young adult book (assuming the reader is likely naive about transsexuals), but never becomes didactic, and is quite realistic in both positive and negative ways.
I prefer not to give away anything else about the book, so let me just end this by saying I liked it, and read it in one slightly-interrupted sitting despite having plenty of other things I really should have been doing.