Originally Posted by YelenaDembo
I study my own theory which I chose for myself and gathered from different books, I solve puzzles for my level, study games of world champions, and solve studies. So, generally work on all chess. Sometimes I vary and study middlegame from books. Years ago, when I wanted to improve from 2300+ elo, I studied 5 endgames books

What were the 5 endgame books? Should I also study endgames to improve my chess, or should I just stick to learning new opening lines?