The Naked Warrior, by Pavel Tsatsouline, is about getting strong using bodyweight exercises. Not endurance (ability to do work repetitively) or power (use strength quickly), but gaining raw strength (ability to do maximal efforts regardless of speed or repeatability). That's rather uncommon, as the most common use of calisthenics is to get "ripped" - lose fat while maintaining muscle - or to get endurance - the ability to crank out dozens and dozens of a given exercise.
The focus is on two bodyweight exercises - the one-arm pushup, and the "pistol" - otherwise known as the single-leg squat. That's it - according to Pavel, these two exercises are really all you need if you do them right. This approach is something he's done before and since - Enter the Kettlebell focuses largely on two kettlebell exercises. Power to the People has you side press and deadlift, and that's that. This one, a pushup and a squat. I've seen people joke that you only need two exercises, according to Pavel, but which book tells you which two. Joking aside, he does come up with pretty good pairs, although I think this book really could have used a third - a pullup. The book does mention pullups more than a few times, mostly in the context of Greasing the Groove (see below). This makes it more odd - why talk about getting more of them when it's not one of the only two exercises you need?
The book launches right into the basics of generating tension in the body. For both the one-legged squat and the one-arm pushup, you need to keep your entire body tense. It's not enough to be strong, because if you don't keep the body rigid you won't be able to move it through the full range of motion. To do that, you learn step-by-step how to breathe without losing tension, and drills for breathing into your diaphragm instead of your upper chest. Once that's done, you start to learn how to tense up by making a fist, driving your feet into the floor, tensing your abs, tensing your gluteals, etc. It's really a good primer on how to hold tension in your body. Why tension? It's the "pushing a rope" versus "pushing a stick" idea - make your body a stick, so you don't push and push but get nowhere.
The book emphasizes the idea that you get strong though practice, not exhaustion. As a result, it pushes two ideas I'm very fond of myself. The first is the "do it every day" approach. Well, every day but Sunday (they recommend one full day off a week). You pick one or two exercises (like the ones in the book) and knocked off 1-5 reps, maximum half what you can do in one all-out set, and do that randomly throughout the day. You can progress up to doing them hourly, or just do a bunch in a row one day and less the next, vary up the resistance (some days do the exercise with extra weight, some days without, some days easier versions), and so on. You just get good at doing the exercise. You make it more efficient - your body will learn to do that exercise with the minimum effort - and you get stronger - your body adapts to the regular pullups, pushups, squats, etc. by getting stronger to handle the demand of doing them regularly. The term for this used in the book is Greasing the Groove. You can read more about it here.
The Pistol gets a chapter of its own, progressing from easy versions like the box pistol to weighted from-the-deck pistols where you switch feet at the bottom. The box pistol is just sitting back and down to a box, bench, or chair behind you. This allows you to learn the movement without falling down when you reach the point past which you aren't strong enough to hold your balance. Once you've gotten down to curb-level boxes, you start doing them without anything to sit on. This forces you to keep tense at all times and doesn't let you use momentum to finish the squat. From there, you start making them a little harder and a little harder. This section is excellent, and it really does a good job of taking your through each variation progressively. You can follow it from one end to the other and go from pistol variation to pistol variation. As a bonus, the "air lunge" - basically a Bulgarian Split-Squat with nothing to hold your back foot - is included as an easier variation of the pistol for those who need to work up differently. It's also a good change of pace if you've been practicing the pistol a lot.
The One-Arm Pushup, compared to the pistol, gets almost a short shrift. All you can really do is vary the height from which you do a one-arm pushup. Start with a wall, or a table, or a high chair, and do a few one-arm pushups off of that. You concentrate on tension, grabbing with your fingers and learning to pull yourself to the floor with your back muscles (sounds crazy, I know, but it does seem to work), and getting down deep. You keep this up, lowering the surface until you're doing them on the floor. From there, it's a matter of repetition until it's too easy, and then you raise your feet and/or add weight in the form of a weighted vest, chains, or weights in a bag around your neck.
The book is shot through with illustrations, boxed-out pull quotes (text from the same or nearby page highlight and pulled out into a box), and oversized print. This makes it a very text-light book for its size and price. Conversely, though, it makes it very easy to read and extremely easy to refer back to. Trying to remember where he talked about balling up your fists to get more tension and squat more easily? You'll find it thanks to illustrations, pictures, and pull-quotes. But don't expect a huge density of information. What's in there is good but it's spread out across a lot more pages than it could have been. The book also has a lot of call-outs to kettlebell instructors, mentions of how great kettlebells are, pointers to Pavel's students, etc. This isn't really obnoxious or a problem, but it does take up some of the space in the book and you need to go in expecting it.
Content: 4 out of 5. There is more than enough information on the two exercises to progress up to them, and there isn't a lot of useless extras. But there isn't a lot for the price, which is why it gets downgraded a bit here.
Presentation: 4 out of 5. The book is easy to understand and the pictures are great, but there is a lot of wasted space in a short and expensive book. You get the distinct feeling it could be cheaper and smaller and more concise without missing anything critical.
Overall: Like Pavel's other books I've read, it's very useful and practical information in a conversational tone. It's useful and readable. It's also priced way higher than a similar sized book would be. If money isn't an object, they are valuable. But they don't have a good price-to-information ratio. If you want to learn to do pistols and one-arm pushups an damn the cost, get this book. You will learn how, and then it's a matter of work, work, work.