High on my wishlist of yet to be invented Google services is a Co-op version of Google Books with a Delicious Library or Shelfari like frontend.

Here's the idea:

Imagine you have a personal library at home and you want to be able to do a full text search on all the books you own (and who hasn't had that problem before?). Already, the Google Book database is huge, but there is no way to do a query on a defined collection of books. At this point, you can only query all indexed books or search through them one by one (cfr. "Search in this book" in the sidebar).

So, in comes the yet to be invented "Google Books Co-op" service...

Imagine Google offers a personal library interface where you can add and organize the books you own. Have a look at the bookshelf of Shelfari's most active user to get a better idea of what this could look like: http://www.shelfari.com/baum/shelf

Now imagine you could pipe these books' ISBN numbers to our "Google Books Co-op" service (cfr. OPML, TSV and XML annotation format uploads to the current Google Co-op) and then limit your queries to the books in your own library. I think that would be great.

N.B. Also imagine how useful this would be for local libraries: it would allow them to put a full text search of (a big subset of) their collection online in no time!

Wild suggestions and additions welcome :-)

That would be a cool idea! Maybe you could tie in a list of your books like what BillMonk already does and then tie that into your Google Co-op gadget by using an RSS feed of books you own. You just might be onto something there. :)

Example of Billmonk library:
http://www.billmonk.com/public_library/index/20802cf3bac8f6304a12a56980e0950961cfe46d