I read the book very good! Also watched it on Netflix I waited a long time for the movie come on Netflix :)

You may want to watch the documentary "The Reason I Jump". It's on Netflix streaming if you have it. It's about mostly non-verbal kids and what they are thinking even if they can't express themselves verbally. Highly rated by Rotten Tomatoes.com reviewers. Just started watching it.

Just gotta add, I stopped limiting my son a long time ago, because even he proves ME wrong, no matter how long it takes.

My daughter is 5 and still hasn't said any words. She was in early intervention around 1.5 but when diagnosed at age 2 did autism specific therapy along with speech. Now the school working on starting a device for communication. We tried sign language for 3 yrs Ash just cant pick it up. For now i do picture cards that i made myself... The pic has her eating going bathroom etc. Figured easier understand the card with her being in it.
Goodluck to you :)

Our children are all different, you must always hope/believe that they will speak. I was told by specialists/doctors that my son would never speak. Speech therapy, PECS, oral motor exercises, and speech at school helped him gain his speech back, not gonna lie it was hard work.
In the mean time, give them a means of communication (PECS/sign language), with the hopes that they will.