I am actually in the middle of my second O'Connor book just this year . Have already read his book The Hunting Rifle and now his book The Art of Hunting Big Game in N.A. Both are, of course, great. But I am also quite sure if you took the time to read Boddington's American Hunting Rifles you'd find it at least the equal of Jack's great book. Not a hint of commercialism to be found anywhere inside. Simple expert commentary from a man who has shot lots more big game than the great Jack O'Connor.
Give it a try.