I find myself saying this a lot, but I'd recomment "Reassess Your Chess" by Jeremy Silman. His system of examining the imbalances is very helpful for improving positional play.
A book to read alongside "My system"?
Sort:
I would say that Part II of My System might do you more harm than good at this stage of your chess development. You need to learn how to play an open game. Most of the concepts of My System require a closed or semi-closed game. You start making extended knight maneuvers in an open game, and you are going to get clobbered.
I am a novice chess player so I am studying "My system" as a chess basics book. Currently I am at the start of part two of the book, although there were some ideas that I have not fully grasped, and example games (at the end of each chapter) that the author gives are difficult to comprehend.
So, while I am reading the rest of the book, I need some other reading material to possibly understand what I didn't understand in "My system", or maybe a book with a completly different "system" (I have heard that Tarrasch was an ardent opponent of Nimzowitsch). My only point is that this book can be downloaded, since English is not my native laguage and I need to study english chess terminology.
Thank you.