Everyone has their own ideas on what they like and find effective. Here are my choices on best books

Self-Training

100 Endgame You Must Know has 300 exercises with solutions that refer back to the original textbook.

Chess Toolbox

10 chapters on basic topics with good exercises. Excellent explanations on topics that I thought I knew

Crucial Chess Skills for the Club Player vols 1+2

Excellent examples with good practical advice. Vol 2(40 exercises) was great and I just started vol 1(30 exercises)

Game Collections

Kamsky is a fanatic at analyzing and explaining his games. 22 games in this volume.

Openings

GM2B 

Some book you have to have and this is one of them

Dismantling the Sicilian

A bit old but very detailed with nice illustrative games. I don’t play 1.e4 but still this is an interesting book that summarizes a big chunk of theory into one book

The Chigorin Bible

Sokolov covered the plans with classical games and Salgado Lopez did the theory section