Last summer, over 20,000 libraries throughout the world participated in the Big Library Read, the global digital book club sponsored by OverDrive, the largest supplier of digital content to libraries. The summer 2016 pick was Julie McElwain's novel A Murder in Time. McElwain's mystery, which was available for free at participating libraries for two weeks, from June 23 to July 7, saw an immediate and tangible bump due to the program. It was borrowed 240,000 times during the two-week period, and a landing page created for the book, featuring a discussion guide, an author interview, and other information about the book, drew millions of impressions.

This kind of boost is typical for a book selected for the Big Library Read. OverDrive launched the program in 2013, and it's now a regular event on the calendars of libraries throughout the world. A large majority of the public libraries that OverDrive supplies with digital content participate in the Big Library Read, which runs three times a year, in spring, summer, and fall.

For participating libraries, the Big Library Read—the largest of the many digital book clubs OverDrive sponsors—offers a chance to engage with patrons in a new way. Sno-Isle Libraries in Washington, which have participated in the Big Library Read since 2014, have seen various forms of engagement increase dramatically thanks to the program, according to Sno-Isle librarians Jackie Parker and Mike Hawkins.

Parker, lead librarian for readers' services at Sno-Isle, says that the Big Library Read often draws in patrons who don't usually participate in the branch's traditional book clubs. 'I don't think everyone has the time, or comfort level, to engage in an in-person book club," she says. With the Big Library Read, Parker explains, patrons who are more comfortable talking about a book "behind a screen" can take part in a community reading experience.

Because OverDrive provides libraries with ancillary content to engage their readers—marketing materials with information about the book and author, for instance, can be customized for different branches—participation in the program can provide long-term benefits to libraries. For Sno-Isle, the increased engagement with the library website due to the Big Library Read and other digital reading engagement strategies drove long-term use of the library's blog.

Erica Lazzaro, OverDrive's director of publisher services, says that the company works with libraries to provide a 'full service" experience that is as elaborate, or straightforward, as the branch wants. For publishers, effort is made to ensure that contributing a title to the program is easy. Publishers are informed of the kind of book that the Big Library Read will feature—different seasons focus on different categories and genres, and options run the gamut from adult to YA—and can then submit titles for possible selection. The seasonal book for the Big Library Read is ultimately chosen by librarians and readers, who select from a shortlist of titles presented by OverDrive.

Publishers also cite huge benefits to participating in the Big Library Read. Margaret Coffee, national accounts manager at Sourcebooks, has seen firsthand just how much of an impact the digital book club can have on a title. The most recent Big Library Read season featured the Sourcebooks-published novel The Other Einstein by Marie Benedict. A landing page dedicated to the book, which is historical fiction, drew 2.9 million page views, according to Coffee. Sales also spiked. Coffee says that in June, when the book club was running, sales of the book were triple what they were in May.

Coffee feels that, beyond sales, the exposure an author receives through something like the Big Library Read is invaluable. It is, as she explains, the kind of marketing that you can't buy.

'Every publisher gives away galleys," she says, speaking to how publishers try to build buzz for forthcoming books. 'But to get millions of people to look at your book—whether it's for 30 seconds, or three minutes, or they read the entire thing.... That's marketing I can't do by myself."

This article has been corrected. In an earlier version, we mistakenly referred to Jackie Parker as Jackie Barker, and stated Parker's title as electronic resources librarian, which is actually Mike Hawkins' title. We also incorrectly attributed a 270% increase in Sno-Isle's blog traffic to the Big Library Read, when it was in fact due to another program.