Book to read on autism for adults

Hi, 

I am new here so sorry if I have missed a post with this info in. I am a 46 yr old woman and I need some help and advice for my 85 year old Dad. 

My 11 yr old nephew has ASD and ADHD. My sister and I have noticed that our Dad has many similar traits to my nephew and Dad also sees it. Dad has told us that when he was younger he knew he was different and so went to a bookshop to try to find a book that would help explain this but couldn't. Books are the thing he trusts in the most.

Sadly our Mum died in December and she was Dad's buffer in the world and she spent the last few months of her life trying to organise things to make it easier for him. We knew this but not just how much. Dad is super bright (2 degrees, speaks multiple languages, had a professional career) but struggles so much with day to day stuff. We have just about got him a routine that works at home but it's really challenging and he needs us to support with everything outside of eat, sleep, wash, go to pre planned regular activity type stuff. He is now so very anxious and gets totally overwhelmed by things that used to give him joy - like gardening, as he didn't decide what to do he just followed Mum's instructions.

I wondered if there is a really good book, the more intellectual and technical the better, about ASD that we could find for him to read. In part so he can better understand what is happening with his grandson but also as part of a conversation that we need to have with him about his own needs. 

Thank you!