The tournament book of Barman 1905 is one 9f the greatest chess books ever. I am the only person I know who has ever seen a copy! On Polugaevsky, Sicilian Love' is a wonderful book.
Most Under-rated Chess Books

On phone. Will see what I can do when I get home, but I doubt that I will find any links to the Barmen book!! I have had to contribute from it for a few published history writers who would otherwise not have been able to get hold of the material.

Link for the book Sicilian love as a pdf. You can find the print one on amazon I think
https://www.scribd.com/document/350293727/Gueneau-C-Piket-I-Polugaevsky-L-Sicilian-Love-Nic-1995-Miroslav-version-pdf

Generally old books . For example , Grandmaster Preparation - L.Polugaevsky , etc that don't belong in most chess player's library ...
Pawn Power in Chess by Kmoch.
The Art of the Middle Game by Keres and Kotov.

Reshevsky's Best Games of Chess, by Reshevsky. Very old and in descriptive notation, but I learned more from this book than any other. Used copies are available in the $10-15 range.
Chess Endgame Quiz, by Larry Evans. Guaranteed to improve your endgame play. 200 positions -- 50 K+P endings, 50 R+P endings, 50 Q endings, and 50 minor piece endings -- some from studies and some from actual games.
Generally old books . For example , Grandmaster Preparation - L.Polugaevsky , etc that don't belong in most chess player's library ...