In The Guardian, Jordan Ellenberg explains his own way of calculating a book’s unreadability, which he dubbed the Hawking Index. Ellenberg looked at the sections that readers have highlighted on Amazon’s Kindle e-readers, and infers that after they’ve stopped highlighting, they’ve probably stopped reading. Link: https://www.independent.co.uk/arts-entertainment/books/features/books-to-read-unread-tsundoku-hawking-index-malcolm-cowley-antilibrary-a8521901.html