Super System 2 is the updated version of poker guru Doyle Brunson's legendary Super System, published decades ago. This is almost entirely a new book, with all chapters but one written by new authors, for the newer, more popular games.
When the original Super System came out in 1979 it was the first book of it's kind. It was comprehensive on winning strategies for games of the time, and most importantly, it was written by well known and well respected poker players. Many games covered by the original book are not popular, so the updated Super System has new chapters for new games, all written by modern day pros like Daniel Negreanu, Johnny Chan and Jennifer Harman, amongst others.
Super System 2 covers limit hold em, seven card stud, omaha, triple draw, and no limit hold em. For games with a split variant, those are covered to. Brunson has also put in a biography of himself as well as discussion of online poker (though much of this must be taken with a grain of salt as he constantly promotes his own poker website).
The actual content is decent. It's a great book for starters to gain familiarity and proficiency with the various types of poker, but none of the individual chapters are regarded as the best instructional text on the subject anymore. For less common games like triple draw, this is one of few texts that discusses it, but for all the other games better books exist once you're comfortable with the games. The only truly negative thing about the book is that Brunson hasn't updated his no limit tournament chapter at all. He was content to say that as he reread the chapter, he realized everything from 1979 still applies now, and has not changed anything. This is a bit of a let down, and also why there are better tournament books out there (namely Harrington on Hold Em).
Overall though, Super System 2 is still a must-have for the beginning or intermediate poker player. At 700 pages it's one of the longest books out there, and the book would be a good value even at double the price.