From the back cover:
Stacey, Jason, and Maria love listening to Maggie B's Bible stories, and can't stand the idea of all the other kids in town missing out. Her rare gift for story telling held them spell bound for hours, bringing fresh exciting discoveries about God.

Now they're determined to share these tapes with their friends. And Professor Appleby wants to help. But how will they get the kids to come to his mansion when all their parents think he's just a crazy old man?

Professor Appleby and Maggie B, book 3.