Quite simply, the absolutely best endgame book on the market today.
ALL my students love it.
I used to teach primarily out of "Pandolfini's Endgame Course." (This is an excellent book, and actually has much more overall material than the Seirawan book.) But this book is better. There is a lot more verbiage and explanations. GM Seirawan takes great pains to explain the moves and the GENERAL IDEAS of the ending you are trying to learn. Its almost as good as if you walked up to the GM, sat down by his knee and said, "Master, teach me everything I need to know to play the endings competently and well."
The Microsoft Press people have one of the finest teams of editors, proofreaders, etc. They have put together one of the best Chess Book series I have ever seen. I can heartily recommend the entire series.
I am sure if you buy this book and study it diligently, your understanding of the end phase of the game will increase 1000%!
(One minor note: The GM does a little bit of showing off in this book. Example: The ending where he has to calculate the win over 20 moves in advance is over the head of the average IM!! But I think you should expect a little of that from a player of Seirawan's capability. Remember, he was one of the country's strongest Master's well before he was out of his teens. He has won or tied for the U.S. Championship several times. He has been a Candidate for the World Championship and has won 1st Place at many International tournaments. So its not suprising to see a little chest thumping going on.)