Atomic Habits: Tiny Changes, Remarkable Results - An Easy and Proven Way to Build Good Habits and Break Bad Ones by James Clear is live of the best books in self help for happiness category. I am sure the title is good enough to convey what this book intends to do. And, believe me, it does that very well. If you are satisfied with your existing habits, good or bad, and find them generating sufficient happiness in life, then this book is not for you.