After launching in September with invitation-only access for the iPhone, Oyster, the New York-based subscription e-book service, is releasing its iPad app today and opening the service to public download with the offer of a free 30-day trial period. Oyster now offers complete access to an unlimited number of digital books for $9.95 per month on the Apple mobile platforms.

Beginning today, consumers no longer have to wait for an invitation to join Oyster—the service used a soft launch to prepare for the process of scaling up to large numbers of users—and can now download the app from the App store and use it right away.

PW was given advance access to the iPad app and it has been designed to take advantage of the added screen space and the interface. The app offers a gracefully designed display much like the iPhone version with a display organized around book covers with drop shadows, horizontal scrolling and a variety of social sharing functions. The iPad version adds a dark iPad screen background and a larger display of book covers that add expansive new display features to the Oyster reading experience.

Oyster offers access to about 100,000 titles, mostly backlist, from a wide variety of publishers. The service has a recommendation engine as well as an editorial staff that also recommends titles. Consumers have access to an unlimited number of titles and can read up to 10 titles offline.