is a book
It is a Spanish book.
It's a book.
It's a very useful book.
My best friend is a book.
That book is a new book.
It's a great book.
Each person is a book.
El mundo es un libro y cada paso abre una página.
The world is a book, and every step opens a page.
Es un libro demasiado extenso como para que yo lo lea en una semana.
It's too long a book for me to read in a week.