Hey Cory!
I think an e-reader of his own is a great idea!
I think an important thing to consider is - do I want him to connect to the internet with it?
I have a basic kindle, and I like that it's easy to use. I like that I can download audiobooks and play them on headphones or through my car sterio. I can even have the computer voice read aloud a text book if I'm driving or doing crochet.
I like that it's lightweight and the battery lasts a long long time. I like downloading free sample books. I like changing the font for low light viewing.
I tend to use the 'highlighting' function quite a bit as I read nonfiction, and it helps keep me engaged. I find it very fun to see what other people have highlighted.
I don't like that mine isn't backlit so reading at night is 'a production.' I may buy a case that provides light for night. At this point I'm using a LED flashlight, but it isn't relaxing. Still, the covers cost almost as much as the kindle.

I don't like that even though there was an upgrade to include page numbers, I don't see the page numbers.
I don't like that lots of books that I would like to own on kindle aren't availible on kindle. But then again, I tend to like 'unusual' sorts of reading material.
BTW - I'm currently reading Harvey and Goudvis' Strategies That Work: Teaching Comprehension for Understanding and Engagement on my kindle, and also on my smartphone. (I love that it switches back and forth) If you son isn't really enjoying reading, or seem mentally engaged with written material, it's possible that you could read this book and come up with some 'example stories' from your own experience that will help him. I'm mostly reading it as a 'Utopian Society' experience. How I would have loved to have had teachers in the early elementary school years who expected by classmates to have thoughts in their heads, and who were experts in helping those classmates express those thoughts! How I resented those 'reading comprehension' questions at the end of the article that compressed the delights of reading into 'detail catalouging' - as in (made up exgageration): "On the first day of school, what color tie was Dad wearing?"
As Harvey and Goudvis say:
"We work hard to build a community of thinkers, expressers, listeners, and learners, a community where kids and teachers care and wonder about each other's interests."
Ahhhhh - this is what I dreamed school would be like.
Grinity