And while I'm thinking on chess, I'd like to recommend a couple books intended for more advanced players on improving the way they think about their moves. Both are quite good and not so widely known.
Zoom 001 Zero Hour for Operative Chess Opening Models, by Bent Larsen and Steffen Zeuthen. It's a very analytical book intended to impress upon the reader the importance of pawn structure, and why certain pawn structures are good and bad, and methods of exploiting them. It's meant to be a general book that helps you fill in the gap between opening theory and applying it to real world games once your knowledge of the opening runs out.
The search for chess perfection, by CJS Purdy. Not the most known chess player, but quite quite a brilliant chess mind that was good at breaking down and explaining a chess positions and particularly good at putting it to paper. Since this is a forum of gentlemen, be sure to find the original version, and not the censored poppycock that modern retailers are likely to carry.