Yeah, there's already plenty of libraries and library-vendors that offer recommendations (Librarything, OCLC's Navigator). Even some open-source online library catalogs have rudimentary recommendations based on subject categories. Libraries likely don't offer recommendations based on a user's checkout history because of a long tradition of utmost privacy concerning a patron's information.
As a librarian though, I'm much more interested in tracking and understanding uses of scholarly journal articles. Most research in academic libraries occurs online, and the current vendors do little but index and provide a search engine.
