“counter for books / volume” in Japanese is 冊, read satsu, saku (さつ, さく). It is a Grade 6 Kyōiku kanji, taught in year 6 of Japanese elementary school, and appears in words such as 一冊 (one volume).
What does 冊 mean?
本を三冊買った。
Same sound, different character — the classic trap. Compare them side by side: