Black Powder Gun Digest, edited by Toby Bridges.  Published 1972 by Digest Books, Northfield, Illinois, USA.  Large format paperback.  

'Complete guide to muzzleloading guns and shooting; black power shooting today - how to choose and use; collecting - how to get the most for your money; rifles, handguns, shotguns - characteristics, ballistics, accuracy of each; do-it-yourself projects; where-to-buy-it directory; catalogue of all US and Import muzzloading guns and accessories'

This has been read and the cover shows signs of age and use.