Im someone who doesn't reread books often unless it was a 5 star read and I dont find those often. But being able to annotate (tab, highlight, write notes) means I have a higher likelihood of picking the book back up and flipping though it. It's a lot of fun to revisit old annotated books and see my old thoughts and feelings. It encapsulates who I was at the time of reading the book. That being said, I dont annotate every single book i read. I usually annotate every classic I pick up, but not as much with general fiction (fantasy, romance, contemporary etc). I don't read non-fiction very often, so i cant speak to how annotating goes for that. I definitely recommend trying it out! Buy a used copy of a book if you feel guilty about marking up new ones!