A real shame that it is no longer in print (unless you know of a re-print being offered somewhere)! There has always been some question on whether Lincoln shot a Spencer Carbine or what. One source I read awhile back, stated their belief that the actual gun was a .56-46 Sporter, rather than a .56-56, which is what the M1860 Infantry and Navy rifles and the carbines were chambered in.
Happy New Year!