A book is a set of printed pages bound together, usually between covers, containing stories, information, or ideas meant to be read. Books can transport you to other worlds through fiction, teach you about real subjects through nonfiction, or preserve important knowledge for future generations.

The invention of books transformed human civilization. Before books, knowledge had to be memorized or written on fragile scrolls. The ancient Romans created the first books by folding sheets of parchment and sewing them together. After Johannes Gutenberg invented the printing press around 1450, books could be copied quickly instead of being written by hand, making knowledge available to millions of people instead of just a wealthy few.

Today, books come in many forms: novels that tell exciting stories, textbooks that explain math or science, reference books like dictionaries and encyclopedias, comic books with illustrations, and e-books you read on screens. Libraries organize thousands of books so people can borrow them freely.

The word also works as a verb: when you book a hotel room or book an appointment, you're reserving it in advance, like writing your name in a reservation book. If a police officer books someone, they're officially recording an arrest. And when something happens by the book, it means following the rules exactly as written.