The Oyster catalog is fairly large and consists of 100 000 books all of which are still a subject of copyright law. The reading progress and the books will all by synced across the iPhone and iPad.
The app itself is designed to fit the tablet form factor and supports simple gestures like tapping to flip pages that is convenient. The cornerstone for such a service however remains the actual amount and quality of books. Getting publishers on board is a very tough task that Oyster has yet to prove it can achieve.
Rival Scribd for instance quietly launched its own ebook subscription and it’s got HarperCollins on board with all its books. Scribd also has a larger loyal following, and a slightly cheaper $8.99 a month service. Scribd's advantage is its cross-platform support including support for Android.