Chapter Books - the new adventure!

I hadn't even thought of reading Mr. A chapter books. Last week someone I know mentioned that they started reading their child chapter books at 3.5, so of course, I had to go get one for A :) He is, of course, newly 3.5 (on a side note, how on earth do they grow up so fast???)

I have to admit - chapter books have been more of a success on his end than mine. He LOVES them. Though he has no concept of what a chapter means - he tells me he needs to read three every night. Then he sits in bed for 10 minutes and continues to read the book to himself. Then he falls asleep, book in arm. It melts my heart.

I think I need some better suggestions though - we have started with Captain Underpants...but it is boring me a bit - any suggestions for first chapter books?