Google has made around 1.5 million public domain books available for free on mobile phones.
The full catalog is initially only available to US mobile users, but over 500,000 books are available outside the US, Google has announced.
The books have been optimized to be read on a small screen. Unlike the books on the main Book Search site, which are provided as PDF images, the books on the mobile catalog only contain text, which is automatically extracted via Optical Character Recognition (OCR).
Applying OCR to millions of books proved to be a "daunting" technical challenge, the blog post states, because unconventional fonts or even smudges on the pages can lead to garbled translations.Rival Amazon is working to port the titles available for its Kindle e-reader to the mobile platform, a company spokesperson told the New York Times. Kindle has an inventory of 230,000 titles, including many of the latest releases.