To become a good poker player, it's helpful to get some knowledge from books. You can get the best books out there with 37% discount on Amazon. Here are the best-sellers and the considered best books for Texas Hold'em No Limit (the most played and well known variant):
Tournaments:
- Harrington on Hold 'em Expert Strategy for No Limit Tournaments, Vol. 1: Strategic Play
- Harrington on Hold 'em Expert Strategy for No Limit Tournaments, Vol. 2: Endgame
- Harrington on Hold 'em: Expert Strategies for No Limit Tournaments, Vol. III--The Workbook (Harrington on Hold'em)
- The Full Tilt Poker Strategy Guide: Tournament Edition
Cash Games:
- Cash Games (How to Win at No-Limit Hold'em Money Games) Vol. 1
- Harrington on Cash Games, Volume II: How to Play No-Limit Hold 'em Cash Games
These books are classics among poker players, and they sure will make you a good poker player!
And there is a classic poker book written by the legend Doyle Brunson - Doyle Brunson's Super System:
Doyle Brunson's Super System: A Course in Power Poker, 3rd Edition