Dvoretsky's Analytical Manual
Topalov-Kramnik 2006 World Chess Championship On the Edge in Elista by Topalov
The wisest things ever said about chess by Andrew Soltis
How Chess Games are Won and Lost by Lars Bo Hansen
The Survival Guide to Competitive Chess by John Emms
Chess Secrets The Giants of Strategy by Neil McDonald
Chess Fundamentals by Jose Capablanca
I recommend all of the above.

I have also purchased a number of books by and about Kasparov, completing the 5 volumes of his My Great Predecessors series, along with the two volumes of his new series Kasparov on Modern Chess. I also picked up copies of the two books by Stohl and the two Kasparov's Fighting Chess books by Tibor Karolyi and Nick Aplin. I can safely recommend all of these books though stronger players will probably get more out of them.

I love looking at some of the games which are widely annotated and combining the insights from several different annotators such as the Kasparov - Topalov game from Wijk an Zee 1999 which are featured in the Stohl and Karolyi/Aplin book as well as in the Lars Bo Hansen book mentioned above (and several other books in my library).

Two smallish endgame books which I have been using a lot lately are:
The Survival Guide to Rook Endings by John Emms
A Practical Guide to Rook Endings by Nikolay Minev
I recommend both books highly as well.

I’m playing over (not studying) the games from two volumes of The Art of Bisguier. Most of my chess books ended up as bathroom books.

I had a top CC player tell me he finds most of his best ideas using a pocket set while sitting on the pot…at least I think he was serious.

I hope those pieces are secure