Does this still insist on making a copy of all my books on my local hard drive? I have about 10,000+ books on a network share. It would be nice to be able to search through them and download just the ones I'm interested in, but past versions of Calibre require the book to be downloaded to your local HDD before it pulls any metadata.
I don't think so, but there is inbuilt calibre-server which should suffice for most of your needs and apparently it was improved in last version. There is also calibre-web[0] project. And on Calibre's wikipedia page it lists quite a few Calibre related applications which could do what you want.