The fair grew out of a librarian's trade show called the Small and Specialist Publishers' Exhibition (SPEX) that was started in 1971 by Clive Bingley and Lionel Leventhal "as a tabletop affair in the basement of a London hotel", and it was renamed in 1976 to recognize the presence of bigger and more general publishers.

The London Book Fair has grown in size and importance over the years and is now considered as second only to the Frankfurt Book Fair as "a mecca for European publishers, booksellers, rights agents and media trendspotters".

More than 25,000 publishers, booksellers, literary agents, librarians, media and industry suppliers from over 100 countries now attend the fair. Book publishers come to London to publicize their upcoming titles and to sell and purchase subsidiary and translation rights for books from other publishers.

Over 1700 international exhibitors participate in The London Book Fair. The fair itself covers a range of interests and marketplaces within the publishing industry, including rights negotiation and the sales and distribution of content across print, audio, TV, film and digital channels, as well as more traditional forms of print publishing.

The event also includes a dedicated conference, The Digital Minds Conference, held on the Sunday before the main fair, as well as an educational programme of over 300 seminars and events as part of the Love Learning Programme.

Prior to 2006, the London Book Fair had been held at the Olympia exhibition centre, but it moved to the ExCeL Exhibition Centre in London's Docklands that year. Due to generally unfavourable feedback from attendees over the new location, the book fair returned to west London in 2007 and took place at Earls Court Exhibition Centre from 16 to 18 April. For every year since 2007, The London Book Fair has been held at the Earls Court Exhibition Centre.