This hard grain of wheat fell to the earth
To be moistened by caring pain into a sprout.
From emptying of self and travails of birth
Springs new life and fruitfulness when time's about...
3 Kinds of Books

PC: Wikipedia
There are a number of kind of books, but most of them can be classified into three: the guide, the advertisement, the thesis.
1. The Guide is purely informative and contains no argument whatsoever. Most descriptive writings, prose and poetry, fall into these. Legal instruction documents (not court arguments) are guides. Also included are manuals and handbooks. Some religious documents are also purely instructional. The "Why"...