First, I respectfully agree with the other reviewers that Sokolov loves, and even admits (p. 221) that he's a 1.d4, center pawn majority player. That said, with the amazing number of transpositions he covers here, even though they are not often 1.e4, they do cover transposed open (1.e4) semi open (Sicilian, French, Caro, Alek, Modern, etc.) and semi closed (due to the many 1.d4 variations) structures with numerous examples.
I disagree, however, with the audience. The analysis here is not nearly as difficult as a Kasparov or Dvoretsky! In fact, Sokolov gives numerous (very cool) "analysis diagrams" (little diagrams that highlight lines off book/ actual play). I'm a 2100+ player and coach a lot of 1700 and club players that "get" the lessons in this fine book very quickly.
The book is mistitled because, as the other reviewers have noted, it is an awesome opening exploration along with pawn structures and key moves that set up a variety of endgames, which also are detailed. Since Ivan covers entire games in his examples, we get to see hundreds of "what's the best move" snapshots in CONTEXT. There are only four chapters, for nearly 300 pages!:
1. Doubled Pawns (12 structures)
2. Isolated Pawns (10 structures)
3. Hanging Pawns (4 structures)
4. Center Pawn Majority (7 structures)
A weakness in the first chapter is its dependence on a lot of "ancient" albeit awesome games from the 50's and 60's using the Samisch Variation of the Nimzo-Indian. Club players would find shocking surprises by reprising many of these structures, and a lot of wins, but Master and above might find them out of date. On the other hand, if you follow very recent trends, you know that the Nimzo is undergoing a powerful rebirth at high level play, and has some of the most complex lines, comparable on the open side to the Sicilian Najdorf/ Poisoned Pawn (ECO B97) where Black's Qb6 results in very complicated pawn structures, many of which do appear here as variations of b2 (black) "poisoned" and c2 (white) isolated (the line of course uniformly starting with 1.e4 c5,2. Nf3 d6 -- the ECO B90 series, or Sicilian Najdorf).
Sokolov's analysis is simply outstanding. Not only does he bring in "book" differences leading up to various pawn structures, but then carries them forward with not only actual FULL games, but countless encyclopedic "asides" from numerous other games focusing on each "crucial" move that changes the games balance to a win or loss. This guy's mind is nothing short of astonishing and it is obvious that he didn't just throw a bunch of Chessbase references against the wall-- many of the examples are from his own games, and the historic diagrams fit precisely into the middlegame point.
Most players over 1800 realize that confusing the mind with a bunch of opening memorization weakens rather than strengthens play. Although not titled an "opening" book, Sokolov teaches us HOW to study openings-- in context of structure and tactics. Given the positional title and structural focus, we might be tempted to think this is not a tactical book. Don't make that mistake! Sokolov covers tactics in extensive detail with every key move, showing HOW the structure, square and strategy lead up to the fork, pin, discovered check, etc.
One of the subtle touchstones of a good book vs. a great book is whether the author realizes that tactical advantages are ephemeral. This theme occurs over and over in this fine book. In fact, Ivan makes point after point like "There was only a brief opportunity to seize this here," "This is only a quickly vanishing one tempo advantage that MUST be capitalized on within two moves..." etc. From a positional standpoint, there are hundreds of humorous, telling and important positional comments like "Note the miserably passive position of Black's bishop on b7" (p. 262). These little "did you see that?" pointers occur throughout the book, and are like a sweet subtle little elbow by the author to hint at something a great grandmaster missed with a "but I'll bet you'll now notice it."
And pattern recognition is the name of the game, right? If you've read other good pawn structure books like Pawn Power in Chess or Understanding Pawn Play in Chess, you'll find this to be a step up in analysis, but not nearly as difficult as a Kasparov or Dvoretsky, long line, diagram free, Fritz generated behemoth. To the criticisms about too much depth and not enough breadth: guys, if he covered more of the openings, this thing would be in three volumes! Sokolov does a fantastic job FOCUSING on the most common pawn structures, which, by early endgame or late middle, are very similar in appearance regardless of opening, giving value to players of any opening, club level and beyond. If you can only afford one pawn structure book-- this may be a tad extra work, but is THE ONE. If you want to supplement it with a good opening coverage series, without ruining your game by overstudying openings, which many club players do, we stongly recommend Djuric's wonderful Chess Opening Essentials: The Ideas & Plans Behind ALL Chess Openings - Volume 1: The Complete 1. e4 series, especially the recent v.4, which covers the Reti and the English and summarizes many transformations, both open King pawn and closed Queen pawn. As Dvoretsky himself often remarks, once you have general opening knowledge and a good middlegame/ pawn structure understanding (which this volume definitely covers), to move on to Master and beyond you need to study endings, not more openings! This assumes you're well grounded in tactics with lots of practice games, puzzles and analysis.
For highly advanced players, Ivan also gives a lot of "why do you think recent (2008 or 2009) play favors 1.xx, when the older 1.yy leads to better lines in this way... A challenge for and at many levels! Highly recommended, one of the best for all phases of the game.