If you read a lot, and there are two of you (or more) in the household, and you have more than one book on the go at a time (I usually have several, to match my varying moods and broad interests), then the question is: What do you use for bookmarks? A wispy strip of paper may do the job, but it's not very satisfying. A decorative bookmark can have bits that get in the way (I don't want strings and danglies, thank you) or be too thick (I want a bookmark to keep my place and otherwise mind its own business).
The easiest thing to reach for, I've found, is a tarot card (or playing card -- but tarots may be slightly larger though no thicker). The tarot card is decorative enough without any distracting additions, and it's not going to slide around or fall out or seem either too substantial or not substantial enough. And buying a pack of tarot cards in a style you like is much cheaper than buying individual bookmarks. Bookmarks, like socks, tend to go missing. When you've got a pack to draw from, it doesn't matter.