If you happen to be reading this article, you've probably played your house game or two, maybe some online Texas Hold Em. You are also looking for ways to improve at poker. Texas Hold Em is an easy game to understand, but very complex, which you are going to find the more you play.
All books will likely be linked after the article
If playing in money games, you should get Phil Gordon's Little Green Book and study it. After you finish, Harrington on Cash Games 1 and 2. While you're reading, its also wise to be playing online, preferable somewhere cheap. Once you have gotten the hang of both of these books, read Ryan Fee's guide on 6max. This book is fantastic, but uses a great deal of short hand you will get over the first three books. While you're reading and playing, join the forums on Two Plus Two. Post some hand histories and get some feedback on your own game. You can also watch some video lessons, some are available at Deuces Cracked.
If you might be playing in tournaments, Harrington on Hold'Em 1, 2, and 3 are fantastic substitutes for Harrington on Cash Games 1 and a couple of.
Reading these books and forums, a lot of shorthand is thrown around. It is not scientific, really a way for those to talk about common situations. There poker online will rarely be described as a 100% correct way to play a hand, it's more an art form compared to a science. Similar to chess, people have a variety of playing styles, no one is correct.
Phil Gordon's Little Green Book: Lessons and Teachings in No Limit Texas Hold'em by Phil Gordon
Harrington on Cash Games, Volume I: How to Play No-Limit Hold 'em Cash Games by Dan Harrington
Harrington on Cash Games, Volume II: How to Play No-Limit Hold 'em Cash Games by Dan Harrington
Harrington on Hold 'em Expert Strategy for No Limit Tournaments, Vol. 1: Strategic Play by Dan Harrington
Harrington on Hold 'em Expert Strategy for No Limit Tournaments, Vol. 2: Endgame by Dan Harrington
Harrington on Hold 'em Expert Strategy for No Limit Tournaments, Vol. 3: The Workbook by Dan Harrington