Depends entirely on what level you're at, what games you play and what you're looking to learn about. Beginner / intermediate / pro? Tournaments or ring games? Live or online? NLHE / Omaha / Stud?
I've only read Super System 1
, and for my money there are plenty of better books you could get your hands on.
The Stud High-Low section talks exclusively about a form of the game that's almost never played any more (the no-qualifier variant - almost everyone plays eight-or-better these days). It doesn't cover Omaha at all, and it spends a lot of time on both regular and ace-to-five draw, neither of which are played much these days either.
I found the Razz and Stud High sections to be pretty good. The deuce-to-seven and LHE sections seemed pretty good too, but I rarely play those games so haven't really tried applying them.
Which leaves the NLHE section - it's an interesting read, but unless you're playing for high stakes against weak-passive opponents, you can find much better textbooks.
FWIW, while I haven't actually read SS2 myself, all the feedback I've heard is that it's fairly similar. Some sections are updated, I believe it covers Omaha and Stud 8, but the NLHE section is supposed to be pretty much unchanged.
Long story short:
If all you want to know about is NLHE, there are lots of better books. Harrington on Hold 'em
, mentioned above, is kinda the bible on tournament play. For cash games I'm a fan of Killer Poker - No Limit
by Vorhaus. For beginners, you really can't go wrong with Phil Gordon's Little Green / Little Blue Book.
There are others if you want to learn about psychology or tells
or money management or whatnot too.
If you want to learn about multiple games though, SS might be worth a read. In fact, I don't think there are
many other texts that cover games like Razz or deuce-seven. Just remember that it isn't a low stakes text.