The Upgraded Bookmark: 30 Seconds to Easier Reading

The Problem
How do we keep track of our progress in a (physical) book?
Using a bookmark, obviously. The trouble with bookmarks, though, is that they only tell us where we left off within a two-page range, and that’s actually not very specific. It’s slightly (okay, very slightly) annoying to open a book and not know if you left off at the top of the left-hand page, the bottom of the right-hand page, or somewhere in between. The denser the book, the more irritating this is.