I've started collecting libraries (cards) from each place I live. Libraries will often have more than one digital service (Overdrive, Hoopla, Borrowbox), and each library may have sharing agreements with neighboring systems.

I use the Chrome Instant Multi Search extension to search all the libraries+services – about 12 different sites at this point. Between them they have almost every book I want in e-book or audiobook, and by placing holds I can keep a steady queue of books going. Managed 125 books this year that way, the majority of them digital, and free.