A Wrinkle in Time by Madeline L'Engle . It was a dark and stormy night; Meg Murry, her small brother Charles Wallace, and her mother had come down to the kitchen for a midnight snack when they were upset by the arrival of a most disturbing stranger.
A whodunnit with a 15 year old autistic boy being the private dick. One of his great statements: “All the other children at my school are stupid. Except I'm not meant to call them stupid, even though this is what they are.