A clever invention:
It looks to be ideal for use when reading The Rime of the Ancient Mariner.
(Also for people who think ordinary bookmarks are entirely too much trouble.)
I’m not sure how well this works near the start or end of the book or whether it’s enough of an advance over traditional bookmarks to care about, but at least it’s interesting to see such a conceptually simple yet quite novel invention in such a familiar application.
by 
Mar a book by attaching a foreign object? Sacrilege!
My impression is that it’s more like a Post-It Note, no permanent effect on the book. I suspect they show the shelved books with the markers left in them because they want you go buy lots and lots of them, though the cost is too high for that to be realistic.
I just got a set of these and a problem became immediately apparent: they’re not long enough. I’m reading Anna Karenina right now, and after attaching the bookmark to the front and back and opening the book there’s nothing left over to hang down and catch the page.