Heidi,
If he's auditory, you may want to check out HOP's next level. I believe it is computer-based, and I'm not sure if they have books to go with it. But, it does have the audio component. I believe it is called Master Reader. My older sister considered it for one of her kiddos.
Otherwise, you could always check-in to books on tape for summer. I always get the book along with the audio and make my kiddos read along silently WITH the tape to keep that ever-increasing vocabulary and word pronunciation going (as they see and hear the words).
Grandma reads the books on tape for us for each year. She does it as her gift to them. I give her the books and tapes/CD's and the schedule, and she does the reading. That is one way we can cover ALL of the read-alouds in our guides without me having to read them all out loud (from classic to boy to girl interest). I read one each genre, she reads one each genre, and my kiddos independently read one each genre.
Blessings,
Carrie