Belatedly, it is worth noting Roy’s remarks about xISBN in his recent LJ column:
Useful on its own, it can be combined with the bookmarklet concept to become part of a compelling library service. Imagine a library user querying a catalog while viewing a book on Amazon and finding any version of that book in the library. Users will be much more successful than if they searched on a specific ISBN. OCLC has combined the xISBN lookup with the bookmarklet concept and as a prototype service is providing bookmarklets tailored to specific libraries on request. [Library Journal – Big Ideas and Small Solutions]