This a cute bookmark. The Abracadabra has two sides to it and one of them comes inflated. When you place the inflated part in your book to mark your place, the weight of the book deflates it. When you go back to your reading, you need to squeeze the half that's sticking out and this will re-inflate the side marking your book. Presto.
Finally, you can use old Abracadabra bookmarks to make art like the stuff shown here.