I've boxed on and off since 1990 and been an athlete in one way or another my whole life but adding many of Ross Enamaits fitness ideas to my routine have helped me take my conditioning to a whole new level. Ross has a background in boxing so the focus is getting yourself in shape for combat sports. If your active in boxing, mixed martial arts, Olympic or Greco-Roman style wrestling, kickboxing or any other combat sport Ross will help you take your conditioning to a whole new level. Whereas Infinite Intensity, while far from neglecting bodyweight exercises, has a lot of stuff with dumbells, Never Gymless focuses on bodyweight/calisthenic exercises and various routines using and variations of the exercises in this book. In his books he also goes in depth with interval training, circuit training, wind sprints, jumping rope, plyometrics, isometrics, sand bag training, there's even stuff on exercise bands. But whats really important is not just the individual exercises or routines , but the ideas pertaining to getting yourself in condition, and how they relate to combat sports. I don't care if your a world champion fighter or at an elite level of fitness, the workouts laid out in his books will kick your ass and take your conditioning to a new level.
I think the only thing I disagree with him on is he downplays, if not out and out excludes distance running opting for interval runs and wind sprints. While I agree 100% that intervals and sprints should be a part of a fighters routine I can't help but remember that the greatest feats of conditioning I have ever seen in a boxing rings conditioning regime had more to do with distance runs than any other facet of training. Ali and Fraizer in their fights, incredibly conditioned fighters like Henry Armstrong or Ray Robinson, and Rocky Marciano who was probably the best conditioned heavyweight ever and he would sometimes run as much as 15 miles in a day while training for a fight. So while I agree that sprints and intervals should be used, and yes there is such a thing as doing too much running, you can't really argue with greats like those whose conditioning surpasses any boxers fighting right now that I can think of.
He also includes a chapter on nutrition in Never Gymless, which instead of focusing on for lack of a better phrase "sports nutrition" he focuses on long term health going into the dangerous gmos, the harmful additives/chemicals that are put into the food, pesticides used on the crops, hormones and other drugs given to the livestock and the harmful effects and why they should be avoided. He gives alternatives (he's big on organic food) to the poisonous products while still being realistic and not fanatical.
I highly recomend both Infinite Intensity and Never Gymless. If you want to get in shape to fight both are the best money you will ever spend.