Bee and I visit my family overseas for a few weeks every summer, and end up reading a lot of books. With physical books we could just hand them back and forth, but with Kindle books you can only loan them to someone once. So we just started sharing a single account for buying Kindle books... it's a lot easier that way. Hopefully one day, Amazon will support multiple sub-accounts just like Netflix does.
Do you share your Amazon account with your SO?