I highly recommend the Henry and Mudge books, because for my son they are just on the border of him being able to read most of the words but still needs a little help from me. They have small chapters and the pictures are great in helping my son decode words that he is having trouble with. He is a visual person and looking at the pictures helps him read the words. It is amazing to see how his learning process is, that is one of the reasons why I chose to have him do school from home.
If you are interested in the Henry and Mudge books, here is a link to the first and second book.