A book fair is a sales event which focuses on the sale of books. Book fairs may be standalone events, or they may accompany a larger event, in which case they may be thematically related to the event. For example, at a foreign relations convention, an accompanying book fair would probably stock books related to foreign relations topics in some way or another. A book fair is often a great way to pick up a wide assortment of books at reasonable prices, and book fairs sometimes provide opportunities to meet authors, people with similar interests, and publishers.

A book fair is generally held in a very large space, like a field or a concert hall, to accommodate the stock of the various vendors who attend. Vendors typically pay a nominal fee for vending space, which may include a table, lighting, and space to lock up at night, and in some cases vendors also pay a percentage of their profits to the organization holding the book fair. Attendees can wander the aisles, buying books and either carrying them or asking the vendors to hold them for later pickup.

In the publishing industry, book fairs are held year round in varied locations, and they are often associated with trade shows. These book fairs give people in the publishing industry a chance to interact with other, see what other publishers are offering, and to meet authors. For the staff at these book fairs, the event can be a fun way to get out of town and to network with other people in the industry.

Many book fairs are simply open all day, with a listing of organized events like talks and book signings listed in a program or at the door. Author events are often used to publicize a book fair and to increase attendance by making the book fair appealing to consumers. Such fairs may be held over the course of several days, especially when they are associated with big conferences and similar events.

It is not uncommon for a book fair to have a theme. Antiquarian booksellers, for example, may hold periodic book fairs which allow consumers to buy from numerous sellers, and such fairs often provide excellent opportunities to pick up rare and interesting books. Educational book fairs may offer resources to teachers, homeschoolers, and students, often at reasonable prices, while book fairs can also focus on topics in the sciences and humanities as well.