- Unicorn Rescue Society series by Adam Gidwitz
- Ben Yokoyama Cookie Chronicles series by Swanson and Behr
- Wings of Fire series by Tui T. Sutherland
- Wow in the World books by Mindy Thomas and Guy Roz (they have a companion podcast that’s absolutely bonkerballs as well!)
All of these have a nice mix of comedy and mischief/adventure that he might enjoy.
Seconding the mythology recommendation! My nine year old loves d’Aulaires’ Book of Greek Myths and was stoked to find a new podcast called Greeking Out by National Geographic Kids. She’s been listening to it practically everyday, and we just picked up the companion book from the library this weekend.