I also highly recommend libby, which lets you check out ebooks and audiobooks from your library. I don't have a kindle myself, but this help article says it's supported "Reading Kindle Books on a Kindle ereader"

You can also add multiple library cards, so if you wanted to go crazy you can find libraries that let you sign up for a card even if you don't have a local address and get access to both library's collections to read on your Kindle