From the OverDrive Digital Library Blog:
The Circulation APIs will allow approved partners to request checkouts, downloads, holds, and returns from within their own discovery interface. This means users will now be able to browse and search their library’s digital collection, see what’s available and check out a title or place a hold all without ever leaving the library OPAC.
Critical to this new technology is OverDrive’s Patron Authentication API which will enable partners who can authenticate patrons to interact with OverDrive services to execute circulations and to acquire OverDrive account details (i.e., “bookshelves”) about their patrons. This means that patrons will also be able to access their OverDrive accounts, again, while remaining at their library’s website, alongside all of the other materials on their library account.
See Also: Other OverDrive APIs