I agree with Retguvvie98, the earlier version is difficult to understand. And is truly written for much stronger players and not for novices. Even after years of playing, I still find the book hard to understand and comprehend. I would like to increase my rating but I fear this book is not going to help me in the short term. I am keeping it around because its a rare found and I hear much praises about this book. It yet something I can use but I am hoping one day!

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I picked this book up about 5 years ago and have to say it is my favorite of all the chess books I have. It helped my game probably advance 200points. Nimzowitsch was a genius.

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I had a copy of the original edition, and have not seen the 21st Century edition - co-edited by Seirawan.   About the original I can say:   Not as easy to read as one might hope, this is written by a GM for other GMs and will be difficult for lower class level players to understand and employ the concepts.  If they can, however, they can expect to see a major improvement in both the quality of their games and in their ratings.

This edition, co-edited by Seirawan, if written more in his style, will likely be a lot more readable and understandable and easier for everyone to employ the concepts to improve their games.