General terms:
* Nonfiction: This is the broadest term and encompasses any book based on facts, not fiction.
* Informational book: This emphasizes the purpose of providing information.
* Factual book: This simply states that the book is based on facts.
* Reference book: This refers to books designed for quick lookup of information, like encyclopedias or dictionaries.
More specific terms:
* Biography: A book about a real person's life.
* Autobiography: A book written by a person about their own life.
* History book: A book about past events.
* Science book: A book about scientific topics.
* Textbook: A book used for instruction in a specific subject.
* Documentary: This term is more often used for films, but could apply to a book that presents a factual account of a specific event or topic.
Ultimately, the best term to use depends on the specific content of the book.