Classics like 'Super System' and 'The Theory of Poker' definitely have their place, but this book was superb in telling me what I wanted to know: as a serious but 'casual' player of holdem, where was I going wrong, and why was I only breaking even, despite generally playing the big hands well. He explains it incredibly clearly and precisely, as well. In one paragraph, he pinned down something which had been bothering me (and in retrospect, costing me a lot of money): even with a pretty large pot, it is not worth calling a bet on the flop with second or third pair, unless you have an overcard or flush/ straight draw. Although you have five cards out of 47 to improve (call it 9-1 odds) with one card, even if you do improve, there is a serious danger that you don't have the best hand, and it is simply not worth playing. Similarly, he drives home another point which had been bugging me: I've definitely been semi-bluffing too much. Doyle Brunson might semi-bluff with an inside straight, but he's a world champion, playing against high level players who often fold. You have to dramatically reduce the level of bluffing against low level players, when there are three or four left in the pot and at least one of them will call. (Doyle himself makes this point in 'Super System'.) Conversely, you may be suspicious that someone else is bluffing, but it doesn't have to be _you_ who calls them every time; 'implicit collusion' between the other players will stop bluffers running away with the game, and you'll get the chance to raise their bluffs in time, when you have the cards to do so.
All in all, Lee Jones' book has crystallised things that I had begun to suspect from playing low level games, but hadn't fully thought through yet. I also like the way he has extensively used computer simulations, in addition to his own experience and other players' experience, so I can feel confident that when he recommends certain opening hands, it's based on solid research. I can't wait to put all his advice into practice.