These 12 best-selling self-improvement books, spanning four decades, have helped readers take important strides and improve their well-being. What Readers Say: One reviewer writes: "I initially avoided this book out of concern that it was one of many under-evidenced self-help titles. What Readers Say: One reviewer writes: "The quirkiness of this 12-month plan for a focus on happiness distinguishes it from other self-help books. What Readers Say: One reviewer writes: "I have read a lot of powerful books about mental toughness, and this was by far the best one I've read. What Readers Say: One reviewer writes: "Feel the Fear and Do it Anyway has helped completely shift my mindset around courage and personal development.