Thanks for the responses. Please keep the recommendations coming!
Despite what I said about openings, I will have a serious look at
The Berlin Wall. If it is true that it is as instructional as you have all said, I'm sure I will enjoy it. I do play 1.e4 e5 sometimes as black, and having an endgame-opening handy might be an effective weapon in certain cases.
Forcing Chess Moves also sounds like a good idea. How does it compare to
Perfect Your Chess by Volokitin? I am halfway through that book and it has given me a tough time in places

.
I am also strongly tempted by Aagaard's
Attacking Manual. The more exercises, the better.
I like Yusupov, but I am not sure I would learn much from
Build Up Your Chess Vol.1. I am 2265 FIDE, and the sample chapter I saw looked a bit simple.
As for the
How to Play Chess Endgames book, I have it and heartily recommend it to anyone, even if they do already have
Endgame Manual and
Fundamental Chess Endings. These make quite a nice set, and will keep you busy for a long, long time.