A friend of mine had one, and I wanted it too: the Thumb Thing. It’s an ingenious invention for reading in bed (or in the park and on the couch). With your thumb in the thumb thing, you effortlessly keep your book wide open.
The only drawback is that it left tiny indentations in the pages of my Freud where the edges of the wings (marked “side” in the diagram) touch the paper. But, hey, that’s the price of comfort.