My poker bookshelf is biased by the fact that I'm only interested in playing NLHE, so I haven't read Super System. I do recommend Harrington's books, especially Tournament I & II. Haven't read III (the workbook), but my take on the books in general is read 'em, play for a while (a year in my case) come back and read them again. Does the table confidence some good to see that the way you want to play them is often what Harrington says is right.
Phil Gordon's Little Blue Book is a good read, but a mite aggressive for my taste. Calling up to 5BB raise with any pocket pair? He probably has the table image to play that +EV, but I don't.
Collin Somethingorother's SnG Strategy book is great. I love books that are deep (everything you want to know about single table NLHE tournaments) instead of broad (a smattering about every poker game
known to man).
I also have the 2+2 Small Stakes book. Not as happy with that one, 80% or so because it's biased towards Limit, which I don't really want to play.