I would say if his difficulties are mostly social, that's a good clue (given the prior suggestions from people who know him) that he might have Asperger's. It is, after all, the "social difficulties" end of the spectrum.
My DS8 is 2E with Asperger's, and the school does a ton of social skills work with him. They have "social stories" that they do in the morning before school, depending on what he is having trouble with at that particular time. The most recent thing has been involving voice level training -- showing him what is a "5" voice and what that is for (emergencies), what is a "3" level voice and what that is for (normal speaking inside), and so on, and practicing. He has had training on how to handle it when he thinks he's being treated unfairly (which is a lot), and when people tease him, and how to ask someone to play, and many many other things. There is a group sometimes, but mostly he works with a counselor one-on-one. They have made arrangements in his classrooms for what he can do when he is overwhelmed (with noise or whatever) or when he is bored or when he is angry, so that he can go to see the counselor, or put his head down on his desk, or go off in the corner and do something else.
I'm sure someone else has book recommendations, but ours are mostly done through the school and through his outside counselor.
