I'm delighted to know about this, but I wonder how long until they close this hole?

I've often wished our library had amazone style reviews and recommendations.

I doubt it's a "hole". More likely a partnership, something OCLC calls:OCLC WorldCat partner
Are there other OCLC WorldCat partners providing this service?

Chuck

Be warned: OCLC is not a complete list of US libraries. Many large academic libraries in particular are not on it.

However, most of these libraries have free online catalogs of their own, so while you have to check library by library, it's still something.

OCLC is mostly a convenience for checking many libraries, especially public libraries, at once.

But once you've found a listing for a book, check that library's own online catalog to make sure it's still there: OCLC is not always up-to-date, especially in taking out listings for books that were moved, lost, or (shudder) discarded.