This book helped elevate my game massively. I was often losing won positions in the endgame without knowing why. I was pleased to see each theme tackled clearly and simply with good explanations. Yes it does explain opposition and critical squares, as well as countless other essential endgame ideas. Thank heavens for that!!! I read it avidly from cover to cover, unlike other endgame books I've got that just bogged me down with unexplained reams of moves. If you already know the essentials of chess endgames, then this may not be the book for you, but if not, I'd strongly recommend it! What I didn't do though is tell my housemate I'd read it, he couldn't understand why he suddenly started losing! sorry mate ;-)