If you shoul choose one endgame book for reference

For a complete endgame reference I would choose "Fundamental Chess Endings" by Müller/Lamprecht.

Why? Look at this video. What book lies next to Magnus Carlsen? :)))
www.youtube.com/watch?v=EY27lgnPKWI

Have been working with that tome since November 2018. About two thirds are done.

Kasparov recommends "Dvoretzky's Endgame Manual" for beginners and professionals alike.

I read it. It's is rather for pros.

Dvoretzky's Endgame Manual on chessable. i hate reading