He would probably enjoy non-fiction graphic books? If so, there's a relatively new series called Science Comics. There are only a few out so far, but the boys LOVED Coral Reefs. A few more are slated to be published later this year.
There's also a large series of graphic books called Building Blocks of Science by Joseph Midthun. Our boys (DS6 and DS5) loved Gravity.
We've also started reading the chapter book series titled Horrible Science by Nick Arnold. So far, they love Disgusting Digestion. To your point about anatomy though, most are not biology-related. And while they're chapter books, they are generously illustrated.
And again I know you said he's not into anatomy, but I have also found the graphic comic Human Body Theatre to be terrific. We got it from the library but now I'm going to buy a copy for the boys (DS5 kept it in his bed every night!). Though come to think of it, the "master of ceremonies" is a skeleton, so you might want to skip that one.
