Worldreader has made this remarkable progress by targeting a niche that is beneath the notice of the commercial ebooksellers, namely feature phones. Yep, that super cheap phone in some of our pockets is more capable than you might expect. It's more than able to run a Java-based app which can display ebooks.
This video from last year's TOC Bologna shows the app in action:
The app was developed by biNu, a mobile app developer that specializes in offering feature phones a near-smartphone functionality. biNu pulls this off by offloading much of the processing to the cloud. The platform compresses the mobile data so any phone can have a smartphone-like speed.
A feature phone is usually much cheaper than a smartphone and thus far more accessible in the poorest countries. That's why feature phones are far more common than smartphones in Africa, where there are about 15 million smartphones and nearly 500 million feature phones.
Worldreader reports that users are spending 60,000 hours each month reading on their mobile phones, and in January they read over 19.5 million pages. About 100,000 readers are power readers and are using the app more than 20 times a month.
They certainly have plenty of free content to choose from. Worldreader offers a library of over 1300 free ebooks and stories from a variety of publishers and organizations including the CK-12 Foundation, Harlequin, Project Gutenberg, Pearson, Ripley's Believe It or Not!, the U.S. State Department, and the World Health Organization. Many publishers have provided the content free of charge because they value the work that Wordreader is doing in promoting literacy.