Most opening books cover reams of variations. This two-volume work contains almost 250 annotated games, sorted to illustrate critical themes in the Sicilian Defense throughout the game. Polugaevsky, a lifelong devotee with both White and Black, covers opening disasters, theoretical disputes, typical attacking and defensive methods, common sacrifical themes, the differing values of each of the minor pieces and the different open files and diagonals, and prototypical endgame situations for those who survive that long. The annotations at times focus on concrete variations, because as Polugaevsky points out many times, this opening is for people who don't mind calculating variations. But about half of the annotations also describe in prose what the two players are thinking and the relative importance of the goals each is trying to achieve.
The end result is that by the end of the second volume, the reader understands the ideas that remain constant throghout the Sicilian Defense, regardless of the variation played or the state of opening theory. This puts the player in a much better position to survive and prosper in unknown positions, refute the opponent's novelties, and carry the struggle forward with success regardless of which color he or she is playing.
It would be hard to imagine a more effective way of learning the Open Sicilian. Whether you prefer the Najdorf, the Dragon, the Kan, the Sveshnikov, the Paulsen, or the Scheveningen, you will find plenty of insights and meat here.