DD loves Magic Tree House and Magic School Bus Science chapter books, too. For a more complex story with equally complex vocabulary that you might read to him, you could try The Indian in the Cupboard. DD loved it! We're on the third in the series.
Some other series that DD has liked reading to herself:
A to Z Mysteries
The Secrets of Droon
Weird Families (My Mom the Pirate, My Dad the Dragon, etc. by Jackie French)
Nim's Island (only 2 in the series)
The Time Warp Trio
I don't have any recommendations about the theme you've asked for, though. I often find it hard to find books dd likes with the topics she likes. A to Z Mysteries, Magic Tree House and Magic School Bus have had at least 1 book that has DDs specific interests. I guess the Weird Families series did, too (she loves pirates).