This is a translation of a successfeul Czech book with more than 1000 problems. The problems can be used to prepare for the International Mathematical Olympiads or the Putnam exam (a prestigious math competition). Each topic contains brief theoretical discussions that are immediately followed by carefully worked out examples of increasing degrees of difficulty, and by exercises which range from routine to rather challenging problems.
From the reviews:
MATHEMATICAL INTELLIGENCER
"I have nothing but praise for this book, and I can't imagine a mathamtician who wouldn't want to own it."
MAA ONLINE
"This book contains over 300 examples and then over 700 exercises for the reader. The authors have even included a fourth chapter with hints and answers to the exercises. So, even if the solution isn't given in the back, at least the reader will have some hint about which direction to start looking. The book provides a nice introduction into many of the problems-solvers' 'tricks of the trade.' There is a lot presented here, so the reader (especially an undergraduate) may want to take the following approach: read just a few pages at a time, work out some of the exercises, then take some time to digest the material before going on."