Well a book that you have to read if you want to be a pro is the Super
System by Doyle Brundson. Some people would say that its a bit
outdated, but it covers a lot of the fundamentals and also a lot of advance
points. Other than that there is the book of Daniel Negranu and there are
a lot of others, but those are some of the most known books for texas
holdem. But I consider the most important thing to be expirience, since
thats what gives you most of your knowledge, plus you can always
talk to the people on the table about the different techniques.