Marcelo in the real world by Francisco X. Stork
Seventeen-year-old Marcelo Sandoval is on the high-functioning end of the autism spectrum. He is comfortable at Patterson, his school for students with different abilities, and is looking forward to working with the school's horses in the upcoming year. His entire life changes the summer his father insists that he work in his law firm's mailroom-the "real" world-if he wants to return to his school in the fall. Marcelo learns, with the help of his compassionate co-worker, Jasmine, and a case that he is drawn to after finding a picture of a girl with a half a face, that not everything in the real world is as it appears.
Marcelo harbors an obsession with religion (he regularly meets with a plainspoken female rabbi, though he's not Jewish); hears "internal" music; and sleeps in a tree house. But Marcelo sees things are they really are and knows when he finds a photograph that an injustice has been done by the law firm his father owns.
I've read several books now (or I should say listened to as all have been on CD) Curious Incident of the Dog in the Night-Time and Speed of Dark and think I found this the most compelling as Marcelo seems like a real person who you could imagine working in your office or seeing in your neighborhood. I've enjoyed all these novels and really found this story engaging.