An old or rare book, often of historical or scholarly value (a classic or collectible book).
その店には珍しい古書がたくさん並んでいた。
The shop had many rare old books on display.
古書展で江戸時代の版本を見つけた。
I found an Edo-period edition at the antiquarian book fair.
研究者は古書を調べて当時の慣習を明らかにした。
The researcher examined old books to clarify customs of the time.
A secondhand or used book (sold as a used copy); condition varies and it's often inexpensive.
ネットで安い古書を買って漫画コレクションを増やした。
I bought cheap used books online and expanded my manga collection.
古書店で気に入った古書を見つけたら、状態をよく確認しよう。
If you find a used book you like at a secondhand bookstore, check its condition carefully.