Dan Gutman's books (The Genius Files (series), Flashback Four (series), a variety of sports-related realistic fiction). TGF has a nice road trip/US geography element to it, plus spies, GT protagonists. FF has historical elements. DG was a teacher (social studies, I think), which adds some fun factoid/edutainment qualities to his writing.
Also, DC picked up Call of the Wild, and really enjoyed it. This was in the midst of a similar Warriors/Redwall phase.
We also liked the Asian Children's Favorite Stories series (Chinese, Japanese, Korean, Indian, etc.), which is a collection of folktales from traditional Asian cultures.
(search Amazon for "children's favorite stories", and most of the series will come up) Beautiful illustrations, too.
