Zachary Elwood's book Reading Poker Tells has been called the best book on the subject of poker behavior by many poker players, both amateur and professional. This is the first book in his poker tells trilogy, following by Verbal Poker Tells (2014) and Exploiting Poker Tells (2017).
This book will teach you how professional poker players analyze the facial expressions, body posture, physical gestures, and verbal statements of opponents in a live poker game. More importantly, it will give you a mental framework for thinking about and remembering poker tells by emphasizing how common situations can be similar or can be different (for example, the big difference between a Post-Bet situation and a Waiting-For-Action situation).
Reading Poker Tells also contains other tips on general poker psychology, including methods for deceiving and manipulating opponents, and ways to stay "unreadable". Many people have said that the greatest value they got from this book was in being able to eliminate some common tells that they were unknowingly displaying.