There are many chess concepts to learn. Some are used more often than others. Learning them is part of the battle, and not forgetting too many is the other battle. Lev says you should focus on remembering the concepts that will be needed the most, and learn the less common ones if you want to be stronger. This book claims to have the most common strategies needed to be a strong tournament player, distilled into 300 problems. He also gives fantastic advice about how you can make your own puzzles and rate their importance and organize them as you climb to new chess skill levels.
Sounds great. As for the delivery, I have not finished the book. I've only done 4 puzzles, and I must say they are very instructive. They are tactics combined with strategy, and he guesses what move I'd have picked, and says why my reasoning is wrong. Each puzzle is dense with instruction, and I've not seen any repeated ideas yet.