book是什么意思

book：作名词指书, 书籍, 卷, 篇, 帐簿, 名册, 工作簿；作动词指登记, 预订, 控告。

例句：

1、This is my book.

2、The book is so difficult that I can not understand.

3、Could you tell me what is the middle idea of the book?