This is the best book ever . . .
What is the best Chess book ever
IMO,
''The Art of Checkmate''
is the best because it has a clear idea of the level of intended readers and what it is teaching and is well organized for those readers to learn what it's teaching. It is also on a compelling and sparkling subject.

Good Chess Books for Beginners and Beyond…
https://www.chess.com/blog/RussBell/good-chess-books-for-beginners-and-beyond
Bishop v Knight: The Verdict - Steve Mayer
I still study from books so will reply just to keep the conversation going...
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I worked thru it last year based on your recommendation and like it a lot. I'd class it as ''very good''. Really like it having complete games with words explaining ideas and organizing the material.
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What Art of checkmate has that is unique is 2 things: 1. Before presenting examples, it gives a simplified position that contains the clues that you want to consider it as a possibility. and 2. After presenting and explaining the mate, it gives puzzles of increasing difficulty where you practice recognizing and doing it. (As best I recall from when I read it around 1970, it also has problem pages where themes are mixed).
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Both of these help a chessplayer at the board make the decision faced at every move.
Bill
OK so a few more ''very good'' books. This means to me that if you work thru it at the right time and right level, you'll immediately improve your game:
Levy, Sacrifices in the Sicilian. I'd say Levy has gotten the right book to help us find candidate moves in a sharp position (that we'd not see otherwise) and gives ''rules of thumb'' about when we should look hard at them. He does not have the 2 things I mentioned above for Art of Checkmate.
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Baburin, Winning Pawn structures: Amazing book about IQP and hanging pawns. Sadly, you need to be extremely lucky to find a copy for a not-crazy price. This is an ''excellent'' book.
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Sokolov has a book on the same topic that is very good. Cant recall the exact title right now.
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For openings: Barden's little , old, outdated book on the Ruy Lopez was excellent in its day.
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For ending study: ''Endgame strategy'' is excellent. Every endgame book of Mednis I've studied has been excellent. Giddins has a book on greatest every ... that is very good and Chernev's book on Capa's endings is very good.
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For endgame repair manuals: to study after I misplay and ending and want to fix it for next time: Dvoretsky is excellent. van Perlo is excellent and Flear''Practical endgame play beyond the basics'' is very good. These are the 3 I go to a lot.
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For the time and for beginners, Fred Reinfeld's ''Complete book of chess openings'' was excellent. It gives a few moves, then a definitive opinion then (usually as best I recall) describes how to play one side after than with a game where the better side executes the plan without real opposition. The stress on ''what o do next?'' after the first 5 moves is what made it an excellent book for uscf 1100-1200 players.
I'm sure I'll think of more. Bill
Which Chess book is the best?