I have tried writing things I don’t want to forget, but I didn’t like it much. I have copied short quotes and added sticky notes at important parts, which I liked, but felt possibly not enough. I tried annotating, but it made me feel bad and disrespectful for the book.
I’m firmly for physically marking books, highlighting passages I like, writing notes in margins, and dog-earing important pages.
Any paperback you get is made with materials that fall apart in something like 10 years. They fall apart whether they’re kept pristine or not. Physical books are a temporary experience that you’re using and becoming part of.
I especially treasure annotations on used books I’ve gotten - nothing cooler than seeing what the high-schooler who had “Heart of Darkness” before me thought of a particular passage.
I do keep a running notes file for passages I particularly like, though.