Harrinton On Hold Em
I have read a lot of books related to theory, bluffing, tells
and general game play within the past year. While all of the books were helpful in the sense that they covered their topics in depth, none of them stepped outside of the box and explained each aspect of the game comprehensively and broke down situations regularly so that you can learn to assess each situation as it's own.
Then I went and bought the Harrington on Hold Em series, and these 2 books alone have helped my game more dramatically than all of the other books that I have read combined. I have a better general understanding of putting players on hands, what bets from different positions are likely to represent, how to read true stregth vs represented strength, etc. The chapters are in depth, but the end of the chapters assignments help you to truly break each hand down to the very last compound, helping you to make correct decisions at the table.
I strongly recommend this series of reading to any player who is looking to improve their game. It has turned me into a winning player instead of a break even player.