The following is a list of good chess books suitable for those who have not yet added "Master" to their chess title...
https://www.chess.com/forum/view/chess-equipment/good-chess-books-for-beginners-and-beyond
As an example of a book which I think would be excellent for someone at your level or those just beginning to learn about positional chess concepts, I highly recommend...
"Weapons of Chess" by Bruce Pandolfini......
https://www.amazon.com/Weapons-Chess-Omnibus-Strategies-Fireside/dp/0671659723/ref=sr_1_1?s=books&ie=UTF8&qid=1483395376&sr=1-1&keywords=weapons+of+chess
It is addressed specifically to the beginner-intermediate chess player audience and introduces the basic elements upon which positional chess technique is built...a nice thing about the book (aside from the fact that used copies are cheap) is that you can read the chapters in essentially any order as the topics inspire you....but it is important to go through the entire book...which should not be all that difficult for intelligent chess players such as yourself...!
Post here what chess books you recommend...