The Book Industry Study Group's Digital Standards Committee has released BookDROP 1.0, which is "a standard intended to support the search and discovery of digital book content on the Web."
Here's an excerpt from the standard's description:
It was first published on December 8, 2008 and was developed jointly by the Book Industry Study Group and the Association of American Publishers. BookDROP defines a set of HTTP transactions between a publishers digital book archive and the websites of the publisher's syndication partners. The overall goal of BookDROP is to encourage the discovery, search, browse and distribution of digital book content across the Web while allowing publishers to manage the quality and availability of their content.
Read more about it at "BISG Unveils BookDROP Standard for Digital Book Repositories."