I wanted to address this problem with my third and final design while keeping the same simple components: a length of string and beads. I also thought I could use a variation of the cinch-type looped knot I often use for things I want to secure, as that sort of knot is easy to release. Fiddling with a few of the corded pendants I sometimes wear resulted in the BookLoop.
For demonstration purposes, here's my BookLoop alongside Marjorie M. Liu's novel A Wild Light:
To make one you'll need a piece of cord, ribbon or string that is four times the height of your book plus two inches (for a standard paperback, that's thirty-two inches.) Don't use anything that is too puffy or dimensional; a simple length of narrow flat ribbon or satin cord will do fine. You'll also need a large bead, button or pendant to serve as the anchor.
Put your anchor on the string, and tie the ends together to make a loop, just as you would a necklace. Once you have your loop tied securely, place it in your book like so:
Bring the top part of the loop down along the spine of the book, and pull the pendant through the end of the loop:
When you pull on the anchor to tighten it, it should look like this:
The great thing about this is you can customize it however you like (and maybe finally do something with all those focal beads or orphaned pendants sitting in your jewelry box.) It doesn't require a lot of expensive bits, it's easy enough for any writer or reader to make and use, plus when you're reading and not using the BookLoop, you can hang it around your neck and no one will ever guess that it's a bookmark.
I really had fun with this challenge, and now that I have three design ideas to play with I'm going to work on variations on the themes and see how I can improve on the original concepts. How do you guys think I did? Let me know in comments.