Meg Mackintosh and The Case of the Missing Babe Ruth Baseball

is #1 of the Meg Mackintosh Solve-It-Yourself Mysteries.
==Book Description==
In the book that launched her adventures, Meg follows a series of notes hidden in her grandfather's house to solve an old mystery of a missing baseball signed by Babe Ruth. The reader is challenged to interpret each clue before Meg solves it.
(Description from amazon.com)