Originally Posted by BelgoSuisse
For SNGs, you should read Colin Moshman Sit 'n Go Strategy.
For MTTs, the 3 "Harrington on Holdem" books.
For cash games, you could start with the 2 "Harrington on Cash Games" books, then Ed Miller's ebook if you ever get to the relevant stakes (i.e. 200nl)
Im not going to disagree on Belgo's recommendation, because the content is great for all players, but take Harrington's cash game book with a grain of salt. I bought this book last year and read it cover to cover, only to find some of his 'example' hands to have very bold mistakes. I did hear that Ed Miller's book is excellent, though I haven't read it yet.