Hello , I believe that all the books of Dan Herington and the Power Hold the Negreanu are the best , although the latter is more advanced! But there are focused books on specific subjects, such as the mental side of poker , so I recomendario The Poker Mindset ... hope this helps !!
There are some basic tutorials on the web that are useful ( in intellipoker for exemple). I don't recommend you to read a lot of books and ever more stupid: TO BUY BOOKS!!. The best way to learn in poker is the experience, the more you play the more you learn, just analyze your wins, losses, watch how elite players play.
One of the big mistakes that people do is to read some theory, then try to including in his game, but they don't know the reasons. you need to have a conviction in your decisions, as real life if you can't decide for yourself, you'll never be successful in any matter.
Theory/Basics/Fundamentals (Must Read)
* The theory of poker by David Sklansky
* The mental game of poker 1 and 2 by Jared Tendler
* All 3 Phil Gordon books (Little Green, Blue and Gold Books)
* NLHE Theory and Practice by David Sklansky
* The poker blueprint by Tri Sgunyen and Aaron Davis
* Power Holdem Strategy by Daniel Negreanu
* Holdem Poker for advance players by Sklansky and Malmuth
* Harrington on Holdem Vol.1, 2 and 3
* Kill everyone by Lee Nelson
* Applications of NLHE by Mathew Janda
* Expert HU NLHE Vol.1 and 2 by Will Tipton (Principles applies)
* Poker Workbook by Doug Hull