Memoirs of a Bookbat

``Honey,'' Harper's mother says to her sweetly, ``You're no longer just a migrant for God. You're on his rescue squad.'' Harper, a highly intelligent teenager given to irony, tells how she ended up leaving her Christian fundamentalist family in this first-person narrative. Ever since her parents have been ``reborn,'' the family has been traveling all over the country in their Roadmaster, speaking out against blasphemy, especially the kind found in C. S. Lewis's Narnia tales, Judy Blume's books and textbooks that teach evolution. But while giving off the outward impression that she is a believer too, Harper is actually a secret devotee of all the books her parents despise (``Are you there Judy? It's me, Harper,'' she says at one point). Harper's eventual escape is partially inspired by her correspondence with an author of fantasy stories. In this very smart (and somewhat acerbic) book, Newbery honoree Lasky ( Double Trouble Squared ; The Night Journey ) combines fictional characters with real-life authors and religious groups (such as Operation Rescue) to create a credible and entertaining story of an emerging independent thinker. Ages 12-up. (May)