I answered a question at chess.com

What is it... the best way to improve your chess?

Capablanca answered your question.

"In order to improve your game, you must study the endgame before everything else. For whereas the endings can be studied and mastered by themselves, the middle game and opening must be studied in relation to the end game."

The book that improved my chess skills the most: "Capablanca's Best Chess Endings: 60 Complete Games" by Irving Chernev. Chernev made the book easy to study because he made it interesting instead of tedious.