7. The Hitchhiker’s Guide to the Galaxy Series by Douglas Adams
Originally a BBC radio program, Adams  blends comedy with science fiction in this tale of galactic travel.  If your teens tell you “Good-bye, and thanks for all the fish,” you’ll know they’ve been reading the series.

8. The Narnia Series by C.S. Lewis
A family of children steps through a secret wardrobe into the world of Narnia. Make believe and heroics blend in these tales of magic and loyalty.