Cruising the Internet, I came across this wonderful elastic bookmark tutorial:
http://www.titus2homemaker.com/2011/10/elastic-bookmark-tutorial/Being a voracious reader, I was intrigued. Here is a bookmark that wouldn't fall out, and wouldn't be as fiddly as a thong-type [uggggg] bookmark.
Now of course, I can't leave well enough alone, so I had to fancy it up. I tried the rubber/plastic necklace cords you find at stores such as Joann's, as well as elastic hairbands from various stores. And one great find of several batches in the dollar bin! The necklace cords are good for paperbacks or smaller books. Hairbands are of various widths and stretchiness, but when I had one that was too big for a particular book, I just tied a temporary knot in the elastic to shorten it.
I dug out my beads, bought more

, and proceeded to make more bookmarks than anyone should be allowed to have. Using large and/or glass beads gives the bookmarks a nice weight. And if the elastic dies, just replace it with a new one!

And this is only the first batch!