What struck me about this book (if memory serves me correctly) is that the author claims that originally, the idea on the show was that Sam's body was at Project Headquarters, and only his consciousness went back in time, and that this premise was changed as the series went on. Yet, in the very first episode, Al tells Sam that the pilot whose life Sam is living is sitting in the Waiting Room. So if only Sam's consciousness is back in 195whatever and the pilot is physically in 1999, then what is Sam using for a body while he files around in the plane and saves the pregnant wife?

I think what it was is that he was sitting there in Sam's body, but I'm not sure. I just made as what I thought, since there was so many conflicting things, that it depended on Sam's job, whether he was there in the leapee's body or not.

But that's probably not real canon....

Then there was the novel where Sam's consciousness was split between two brothers. And the brothers were inhabiting Sam's body. A strange book and thankfully not canon.

That book was by C. J. Henderson and called Double or Nothing.