Humble Bundle Books, the promotional site that allows consumers to pay what they wish for bundles of DRM-free e-books, reported sales of $21.3 million in 2018, up from $15.6 million in 2017, as well as record charity donations. The site encourages consumers to direct part of their payments to charity, and a group of 19 participating book publishers raised a combined $5.6 million for a variety of publishing-related nonprofits.

Humble Bundle was launched in 2010 to offer pay-what-you-wish video game bundles, which attract a mammoth audience to the site, and in 2014 it added similar bundles of e-books. Humble Bundle was acquired by gaming and entertainment news site IGN in 2017.

Kelley Allen, Humble Bundle’s director of books, said that the 19 book publishers were among HB’s top 100 charity donors, which also include video game publishers.

The biggest book publisher donation came from a bundle promotion by O’Reilly Media, which generated $1.3 million for charity. Also among the top book-driven charity donations were Packt ($972,177), Wiley ($732, 885), No Starch Press ($426,083), and Image Comics ($223,439).

Among the publishing-related organizations receiving donations from Humble Bundle promotions were the Comic Book Legal Defense Fund ($220,000), the National Coalition Against Censorship ($107,000), and the Book Industry Charitable Foundation ($100,000). The CBLDF will be a featured charity during February 2019, and its executive director, Charles Brownstein, said Humble Bundle donations have stabilized the organization and allowed it to focus on its mission: defending First Amendment rights. “Thanks to Humble Bundle,” he added, “we’ve been able to create more publications, provide more counseling, and maintain our legal defense team, who are there to respond to First Amendment emergencies at a moment’s notice.”

Allen credited record Humble Bundle book sales to “great working relationships” with the book publishers, which often have to be persuaded to offer digital books without DRM protection. He also attributed the 2018 sales growth to adding “certain genres including technology, programming, the popular maker movement, science fiction, and role-playing game titles.” Among the new publishers that signed with Humble Bundle last year were Chronicle Books, Frog God Games, MIT Press, Skyhorse, and Viz Media.

Humble Bundle released 90 book bundles in 2018, and some publishers released multiple bundles. Tech book bundles generated the highest revenue and included Packt’s January 2018 Python bundle, which brought in more than $907,000 on 64,980 bundles purchased, and O’Reilly Media’s August 2018 machine learning bundle, which brought in more than $585,000 on 42,077 bundles purchased.

Allen said to expect the addition of more publishers and new charities in 2019, as well as more book bundles of RPG and tech books, comics, and nonfiction titles.