Refers to books that are old, antiquarian, or of historical value, not simply secondhand. Often used in contexts like 古書店 (antiquarian bookstore).
His hobby is collecting old books.
His hobby is collecting old books.
This antiquarian bookstore has many valuable old books.
secondhand book; used book
Used for books that are pre-owned, regardless of age. Often interchangeable with 古本, but 古書 can sound slightly more formal or refer to older used books.
See also: 古本
I bought a cheap used book at the secondhand bookstore near the station.
I looked for a rare book at the antiquarian bookstore.
I bought an old map at the used-book fair.
新刊 refers to a newly published book, the opposite of 古書, which is old or secondhand.
counter for books; counter for volumes · volume; book
Compound of 古 (old) and 書 (book, writing).