For me... lol, 118 books.
The Book that helped me the most was a an inexpensive little book called "How to play the Chess Openings" By Eugene Znosko-Borovsky
He was a Russian Grand Master from the early1900's that had a gift for taking a Complicated Precept and presenting it with incredible Clarity.
"It is not a move, even the best move, that you must seek, but a realisable plan."... E.A. Znosko-Borovsky
Just Curious...
How many Chess Books do you have?
Please tell us which ones helped you improve the most or had the greatest impact on your rating.