After reading the amazon ad material, I'm not sure that the making of The Film "The Searchers" is the focus of the book. It seems to be more about the physical abduction and life of Cynthia Ann Parker and the concomitent (ahem) scar upon the American psyche.
Of course, this is the inspiration for the film, but don't expect to find a day by day detailed of the making of it. I believe it will be interesting reading. Just don't be mislead.
We deal in lead, friend.