Another great book
Johan Hellsten's Mastering Chess Strategy is another great book on positional chess for improving players. What I like are puzzles at the end of the book where given the topic, you know what to look for. For e.g. where the topic is bishops, you know that the immediate move and the plan involves bishops.....freeing the bishop, making it active or finding a better square for the bishop or fighting for the long diagonal.See sample page below.
Once the puzzle is solved, one realises that it is so obvious - and I believe one's ability to evaluate a position improves dramatically compared to other books on the positional chess which just shows you a chess diagram and asks you to evaluate. I think the difference between chess novices and chess experts is precisely this chessic vision. The novice looks but cannot see whereas the expert merely glances and understands everything completely. This is where I believe Hellsten's book helps us develop that vision.