Wow, thank you for all your stories and suggestions. I really appreciate them. Yes, we have tried sharing books and info with him... and he isn't interested. So I imagine that he will not be open.
My brother is not independent. He lives at home with our dad, and has been completely dependent on him for the last 18 months. He has lived independently on and off, but he always seems to end up back at home. He has worked intermittently, but seems to have difficulty keeping (and now getting) a job.
He is a wonderful person, highly intelligent, but socially he does have some challenges. Not with forming friendships and being a part of community, but more so in terms of what may be expected of him (such as, following his boss's instructions, rather than ignoring them and doing something different because he feels his way is better... and it might be... but it isn't what has been asked of him, so he tends to lose his jobs that way). He has had only a couple of longer term intimate relationships, but sadly nothing lasting.
He was told he had ADHD, but he dismissed that as a "non" diagnosis. He thinks it is just a way for the pharmaceutical industry to peddle drugs to kids. He is caught up in "conspiracy" theory like nobody's business, and has an appetite for hallucinogenic drugs (and anything that removes him from reality) in large quantities.
Knowing my brother, I don't think he is going to take kindly to his diagnosis. It is most likely that he will dismiss it as nonsense. I am preparing to get some advice from a therapist who specializes in ASD and get more information from there. It has been left unsaid this long, I think it's best to get as much information as I can first, since a few days or weeks will not make much difference.
Finally, I really appreciate the validation to share this info with him. I can't imagine how hard it will be to hear, but I also think that deep down it will make sense for him and that eventually he will be more accepting and understanding of it. I hope he can find some support within the AS community and use the knowledge to his advantage.