The Throne of Fire  - Rick Riordan
The Kane Chronicles don't need much of a review. They aren't going to go down in literary history, but all three were fun to read. There are mysteries to solve, good guys to cheer for, bad guys to beat, and plenty of drama along the way.

I'd say 5th graders and up would enjoy the series the most. There are a lot of characters, including many Egyptian God's with hard-to-remember names, that might frustrate younger readers.