Kindle ebooks allow to share individual insights into the ebooks. E-readers can aggregate their experience of a text, so that anyone can identify those passages that collective wisdom had identified as particularly pertinent. Enough ereaders need to highlight a passage to be visible to others as an aggregate or a reading heat map. It’s a great idea to save time reading ebooks by showing key passages illuminated by layering all readers’ highlights for the same text. More insights into ebooks, e-reading, etc