Agatha Christie at her best! I love how mathematically precise this book is. For lovers of psychology, symmetry, and exploration of human behavior, it is a pure delight to read it. "Why" is the question to be answered here, and the Queen of Mistery is leading us masterfully by our trembling little hands to the unexpected but justified end. Please, please, read it if you have not already done it! But if you have, read it again!