[BetterRed]

Try this

1. write a list of books to a csv file with the Catalogue feature (you may need to add Create Catalogue to your icon bar or menubar)
2. save the csv file to somewhere outside the Calibre library - eg the desktop
3. edit the csv file into a list of fetch-ebook-metadata commands
4. rename as a bat file
5. run batch file

There are more sophisticated solutions involving database queries and some OS level scripting, but this will give you a feel of batch performance

I doubt it will be much faster - the delays are mainly due to the speed of the servers and communications.

It's my understanding that if you do too many books in a batch (I've seen people refer to a 100) the metadata source sites will probably throttle your request, in some cases they may blacklist your IP address for a while.

BR