Subscription e-book service Oyster has announced the addition of about 500 new publisher partners, bringing its library of e-books to more than 500,000 titles. Oyster has also expanded its partnership with HarperCollins, adding 10,000 Harper backlist titles to the Oyster database.

In an interview at the Manhattan offices of Oyster, CEO Eric Stromberg said the venture added content and more breadth to the company's offerings and, although he declined to give precise figures, noted that “the growth in new Oyster subscribers is attracting publishers to our service.” Stromberg cited the Perseus Book Group, which started with a pilot program and increased the number of titles it offers via Oyster earlier this year, and now HarperCollins.

“Harper saw the breadth of titles being read by our subscribers which led to an increase in what they now offer,” he said. Stromberg said that “we’ve also become a meaningful retail channel for publishers,” emphasizing that the service is producing significant revenue for its publisher partners.

Oyster offers readers unlimited access to a library of 500,000 e-books for $9.99 a month. Stromberg said Oyster now offers titles from more than 1,600 publishers. With this latest deal--in addition to adding 10,000 titles from HarperCollins--Oyster also added titles from such publishers as John Wiley, Chronicle, McSweeney’s and Grove Atlantic. Titles include Wiley’s For Dummies series, Black Hawk Down by Mark Bowden and Candace Bushnell’s Sex and the City. Among the HarperCollins’ titles now available through Oyster are American Gods by Neil Gaiman and Beautiful Ruins by Jess Walter.

Oyster also offered some data on the reading habits of its subscribers. During the day about 50% of Oyster subscribers access the service by mobile phone. At night and on weekends most subscribers use the iPad, and the average Oyster user reads about 45 minutes per day.

Among the most popular titles on the Oyster app are Winter’s Tale, Life of Pi, The Best American Short Stories 2013, the Hobbit and Skinny Bitch. In addition, Stromberg said that while romance, mystery and sci-fi fans “tend to read only in their genre,” Oyster data shows that business and general nonfiction readers tend to “read widely across genres.” Stromberg noted that the addition of nonfiction titles from STM publishers like John Wiley “will bring in more readers who read broadly across different categories.”

HarperCollins chief digital officer Chantal Restivo-Alessi offered a positive response to the Oyster service. She told PW that “we’ve had good results and we saw no reason not to support expanding the list of titles available through Oyster.” Restivo-Alessi said the new titles were all “backlist,” titles at least a year old. She also agreed that there has been an increase in revenue produced through the program. “We had a limited catalog through them so there has been a proportional increase. We saw sales that were encouraging.”

Restivo-Alessi also said that Oyster, along with other subscription e-book services like Scribd, offered an overall increase in “discoverability” for Harper titles. “Our books can be accessed across Oyster and other subscription services. We are seeing a bigger uptake of the deeper backlist titles, so we believe that overall, subscription services are a complementary channel that helps expose deep backlist titles.”