1. Does your son have interest in particular topics that you could find books on? If he likes trains, dinosaurs, or boats (or whatever), perhaps you can find him books on his favorite subject.
2. Books by Eric Carle, like "Brown Bear Brown Bear What Do You See?" have great pictures and simple language.
3. My sons like "Are you my mother?" I think the author is P.D. Eastman.
4. This website has some other book ideas:

http://ourlittletongginator.blogspot.com/2012/0...

Here's to many happy reading adventures for you and your little one.

Little critters series is nice, audio books that are age appropriate. I have a kindle and there are nifty turn the page series applications out now too. Peep and the wide wide world on pbs and Martha speaks is nifty.

I like the Sandra Boynton books because they are short, have great pictures, and have a good rhyme scheme. You can usually find them at you local library, but some are available as Apps on the iPad.

My son also likes the "Pete the Cat" books because they each center around a particular life lesson. Similarly, the "Llama llama [red pajama]" series covers a lesson in each book, as does the "How does a dinosaur [say goodnight]" series.

Karma Wilson writes a great series about the Bear and his friends, which center on social skills.

We also checked out "Dinosaur Train" more than once, as well as "The pout pout fish and the big dark"

Our son's book club sent us some great books that are simple, paper back, and promote emotional development. They are by Todd Parr. We have "The Feelings Book" and "It's ok to be Different." The series from When you give a Mouse a Cookie seem to be simple and fun. More silly.

If you are connected with Regional Center they have a great library to you can utilize to obtain things to assist in the progression.