This book is an attempt at describing basic problem-solving strategies. Based on puzzles and mathematical riddles the author tries to teach the general approach of problem-solving, but I think that assuming that problem-solving skills can be taught by reading a book is a bit of a flawed idea in the end.
One has to sit down and do the problems themselves and figure out how and why things work the way they do, especially in mathematics. Also, this book is rather specific to mathematics, even though its title aims at a broader audience. It's about learning how to solve - mathematical problems - not general problems, even though one could argue that there are elements of mathematical problem-solving involved in every other problem and that the strategies learned from there can be translated into other realms.