Readmill partners with Guardian, Atavist and Livrada and adds a free book section to its app

iOS (s AAPL) reading app Readmill added a book discovery feature on Wednesday and also announced three new partnerships with the Guardian, The Atavist and ebook gifting site Livrada.

The new “Explore” section of Readmill’s app lets users download free ebooks from directly within the app. For now, a lot of those books are in the public domain, but Readmill is also working with publishers and independent bookstores to run limited-time promotions through the “Explore” section. At launch, Emily Books, The Atavist, The Pragmatic Bookshelf, Five Simple Steps, Rosenfeld Media and a few others are giving away ebooks through Readmill’s app.

In addition, Readmill has partnered with The Guardian, The Atavaist and Livrada. The Guardian and Atavist are using Readmill’s technology to enable direct sales through their websites; once a user has bought a Guardian Short or Atavist e-single, he or she can use the “Send to Readmill” button to read it from Readmill’s app. And Livrada, which enables users and organizations to gift ebooks, will use “Send to Readmill” for delivery of EPUB files.

The Berlin-based Readmill is growing fast. Over 75 independent publishers and retailers, reaching a million readers, have now enabled the “Send to Readmill” button on their sites, up from 22 in February. “We’re adding new partners almost every week,” CEO Henrik Berggren told me. “We started out trying to convince everyone it was valuable. Now we’re basically only handling inbound requests.”

Moving forward, Berggren said that Readmill wants to expand beyond iOS to more platforms, and also wants to support more types of ebook files (right now, it only works with EPUB and PDF). The company’s launch of support for Adobe DRM last October means users can now read books from Kobo, Nook (s BKS) and Google Play (s GOOG) through Readmill, but Kindle(s AMZN) books still aren’t supported. “It’s very important that we support as many formats as possible to make it easier for the readers,” Berggren told me. “You should be able to open any file.”

Disclosure: Guardian News & Media is an investor in the parent company of GigaOM/paidContent.