We are loving the "Wonder Island Boys " books, which are adventure stories chock full of "science" yet are technically "literature".
There is nothing dull about science with these books, and they are also a nice change of pace from our usual science studies. (They are approximately 7th grade reading level.)
WONDER ISLAND BOYS (scroll to the bottom)
Or they are also available from Gutenburg Press under the author's name (Roger Thompson Finlay) .