For all you No Limit players, the essential book is out, and it's not SuperSystem 2. Dan Harrington just came out with Harrington on Hold'em Vol. 1 which focuses on early to middle stages of NL HE tournaments. It's a must for anyone who plays tourneys or Sit-n-Goes, but since it covers early rounds when rising blinds aren't a factor, it's also applicable to ring games, minus the "survival" aspect of tournaments.
Pro players and the most cynical of poker board posters are calling it the definitive book, and can't believe how much inside info Action Dan gave out. It goes over every factor a player should consider when playing a hand, betting strategies, reading opponent's betting patterns, etc. and has detailed hand examples with Dan's thought process for every step. And it's written in a very conversation and entertaining style. I was just going to skim the first few sections since I'm still concentrating on limit ring games, but I haven't been able to put it down. Now I'm hankering to play some SnG's.
In a few months, there will be a Vol. 2 that covers the later stages of tournaments - dealing with rising blinds, moving up the ladder, playing shorthanded tables, and heads-up at the end. That's totally tournament specific, but anyone who wants to learn about NL, should check out the first book.
P.S. I hear that in Super System 2, Doyle's NL section is barely changed from the first edition, but that Jennifer Harman wrote one of the best things ever on Limit.