I have been looking for a newer copy of this book to share with my eight year old. The book is called ChristopherChristopher and was one I treasured at her age. It’s currently in a box somewhere in our basement; I’llI'll share the publication information and a copy of the cover once I locate my old one.
A Goodreads review of Christopher by Richard M. Koff:
Christopher, on a dare, goes into this deserted house and finds a man living there who has been waiting for him, apparently. He is a teacher, and, through Merlin-like abilities, teachers Christopher about himself and about life in general.