I can verify that Wal Winfer is working on Rook Rifles and the book will be part of his series on British Single Shot Rifles.
I had the pleasure of helping Tom Rowe photograph a bunch of them localy last fall. It was a lot of work but it helped me improve my ability to take pictures.
I will give Tom a call and ask him when they are looking at having the book done. I do know that Tom is rather preoccupied with getting the Pope books out soon.
Cheers,
fallingblock