Thanks for the link!
I bought a book for my seven year old:
Warriors #1: Into the Wild. I've been wanting to try ebooks with him, although this isn't really his type of story. (He doesn't seem to like fantasy, but he does like cats.

)
It also says grades 6-9 (he's going into grade 3) but he has read all of the Wimpy Kid books and according to his teacher, was reading at a fourth grade level last year, so it shouldn't be much of a stretch. (And I'd like it to be something of a stretch since all he *is* reading this summer are illustrated books. Not all comic, but mostly.)
I think he would really like this one:
The Big Book of Boy Stuff, but when I did the "Look Inside", I thought it would make a better paper book that he could flip through and pick out random pages to re-read.