A book that has been previously owned or used and is resold (a used or secondhand book).
あの古い漫画の中古本をブックオフで見つけた。
I found that old manga as a used book at Book Off.
中古本は状態をよく確認してから買ったほうがいい。
You should check the condition carefully before buying a used book.
オンラインで欲しい本の中古本を検索したら、安く出品されていた。
When I searched online for the book I wanted, I found a used copy listed cheaply.