These days, I prefer to read ebooks - they are easier on my wrists than physical books. I live in Portland Oregon, and the local public library system delivers their ebooks through an app named Libby.
Last month, I drove across the river to the neighboring city of Vancouver, Washington and got a public library card there. It was free because they have a reciprocal agreement with the Portland system. I immediately signed into Libby with this card, too.
I'm currently reading a novel by Terry Pratchet that I'd checked out from the Portland library. There was a long queue to get the novel, so I was pleased when my turn finally came, but I'd been busy, and the loan expired when I was only half done reading it. As expected, the book auto-returned itself, disappearing from the app, and showing up in the history as properly returned.
Now here is the surprising part:
The next time I opened the Libby app, it told me that the book I had been reading was available without any wait from one of the other libraries (i.e. Vancouver) I had a card with, and showed me a borrow button to borrow it from the other library immediately. I pressed the button, and the app borrowed the book, and even remembered my place so I could keep reading without any interruption.
Libby had given me a useful feature that I didn't know I wanted!
(Now I want Search in Libby to tell me, when I search for a book, if another of "my" libraries has that book with a shorter waiting queue.)