This book is not really about any secret history, as the background story of Repairman Jack was already revealed in the books in print about him. What it IS is a new series aimed at the juvenile market (old enough to read about stuff they cannot do, young enough to only identify with heroes of their own age). If you can take the book for what it is, a juvenile set in the pre-history (or early history) of Repairman Jack, it is an excellent read.
Now, if you don't know who the heck Repairman Jack is, this is the wrong place to start reading about him. Go to the link here for F. Paul Wilson and look at his bibliography. Read the Repairman Jack books in order, then come back to this one and see if you enjoy it. I certainly did !