The third Percy Jackson book came out a couple months ago. My kids and I love this series! Other good middle schoolish reads are :
Ida B.-
Millicent Min: Girl Genius- Lisa Yee
Circle of Magic by Tamora Pierce (some of her other works may be a bit mature for ten year olds, but I have allowed my 10 yo son to read them)
The Young Royals series- Carolyn Meyer
The Bartimaeus Trilogy- Jonathan Stroud
The Bromilead Trilogy- Terry Pratchett
We recently gifted a young friend with the two Blue Balliett books, and accompanied them with a set of pentominoes, a Mike Venezia "Getting to Know the World's Greatest Artists" book on Vermeer, and a Frank Lloyd Wright paper Robie house model. I think it went over well!