Just thought I'd share my recent experience with the metro.
My research had led me to believe that there would be no more paper tickets (carnets or books to those of us who are ancient), like most mass transit around the world nowadays you would buy a plastic Navigo Easy card and load value onto it. But lo and behold, when using the ticket machine I was offered the option of buying a carnet. And out popped those little tickets, the ones that look like pieces of Trident gum.
They are also accepted on buses, my bus driver was no help but a friendly local showed me how to push the ticket into the machine at the front door. I took Rick's beloved Bus 69 to get to Pere Lachaise, but I joined it in progress at the Bastille so I missed his favorite parts.