Nokia Reading will offer books popular in local markets, but also books in English that have made the best-seller list. Since the Amazon Kindle app is not available to those using Windows Phone, 'Nokia Reading' takes its place and allows those in non-English speaking regions (where eBook sales have been traditionally low) to have easier access to digital books. Additionally, for those who enjoy the classics, many of them will be available for free.
The books will be divided up by genre or by popularity and can be displayed as black print on a white background or as white print on a black background. The latter will save wear and tear on your battery life. It is believed that licensing problems are keeping the app from being offered in the States.
source: Nokia Communications