Winning Chess Tactics is the follow-up book in Yasser Seirawan's Winning Chess series. WCT picks up where the sections on tactics in Play Winning Chess left off. Not too surprisingly, WCT details more subtle or less obvious points about the tactical issues of chess.
The author continues the discussion of the usual suspects such as forks, pins, skewers, and so on, and then explains specific subtypes of these tactics. For instance, in the chapter on pins, Seirawan explains the concept of both absolute pins and relative pins.
An important theme in this book is the notion of combinations and sacrifices. While PWC spoke to the basic tactics, WCT explains how to produce positions in which the basic tactics can be used. For instance, you may recognize on the board the potential for a devastating fork, but what do you need to do to actually attain that position? The text develops the topic of combinations, and how they can be used to reduce the game position to a known pattern, which forces an opponent into a losing position. This amounts to the use of sacrifices, decoys, et al. to produce an advantageous board position.
Although the topics in this book are more difficult to grasp than those laid out in PWC, the writing is still clear and understandable, although Seirawan has a bad habit of trying to be "cute" with his pros. That, however, is merely a minor annoyance and should in no way prevent you from reading this book.
An important part of this book is the copious number of tests. Be prepared to spend a lot of time over the board or with your favorite chess program. The real meat of WCT is contained in the tests, and without working through all of them, you really won't get much out of this book. Many of the concepts that Seirawan attempts to express are found only in the tests. This might sound a bit nasty, but it actually worked for me quite well.
Admittedly, the first couple of chapters were rather tough going, mostly because I found the tests to be very difficult and rather less than transparent. After slogging though the tests in the early chapters, things got better. The big problem I had was figuring out what, exactly, the damn questions were talking about. But, with some perseverance, it wasn't long before I passed that hurdle. That isn't to say that the later tests were easy, but at least they made more sense to me.
After the discussion of specific tactics come seven chapters dedicated to the games of some of the greatest chess tacticians of history. What can I say about this? These games are, in short, mind-boggling, beautiful, and testosterone injected feats of tactical brilliance. There's not much point in me describing them, so I'll simply point you to one of these historic games for you to evaluate yourself: Paul Morphy vs Duke Karl / Count Isouard .
Although this book is the second in a series of books, it is designed to be readable independently from the other books. However, if you haven't yet read Play Winning Chess or some similar introductory chess text, you may be in over your depth with WCT.
Arguably, I haven't actually finished my first pass of WCT. The last three chapters are nothing but tests, and I'm working through them a few at a time while I dig into Seirawan's third book.
At any rate, I learned quite a lot from Winning Chess Tactics and it will take several more go-rounds (at least) before I've plumbed the depths of this book. I highly recommend WCT to anyone that is willing to get their hands dirty at the chess board.