Online bookseller Erapublications has an API for its in2Era web service for selling ebooks through online distributors. According to its documentation, this RESTful API, which requires an authentication key, integrates its catalog onto your site. Distributors get a cut of the sales.
The API allows you to set up and manage subscriptions to educational content (including designing the subscriptions), brand them with your own logos, and handle transactions in your own language and currency. In2Era's content is then embedded into your site in a manner similar to how youtube videos are embedded. Distributors are awarded territories and prices are negotiated based on the nature of the territory.
In2Era outlined the basic mechanics of how it works on your site from the user's point of view,
"Users must be able to login to their own account with a username and password. Once logged in, they should be able to purchase a Subscription to an online Product. This can be done in the same way as any other purchases. Once they have paid for their Products, the Subscription(s) they have chosen will be associated with their User account for the duration of the Subscription period (e.g. 1 year). When Users login, using their username and password, they are able to access the resources that they have subscribed to."
Since the site is only updated as new product is added, distributors are encouraged to maximize performance by caching the product records. Updates are sent to distributors so that they can send out notices of new product as it becomes available.