This seems to be about scribbling in your own books though, not someone elses.

Writing in the margins is a thing I believe many a scribe has done for many generations

It's recognized as a study aid. Especially if you're re-reading or studying a lot of material on a subject and need to go back. You can easily see what your past self was thinking or maybe quickly find a part you found interesting.

It's fundamentally useful to write up your own books.

I never found useful to write up my own books. I find it ruins them for other people, too.

Suit yourself.

It is just one tool among many for the acquisition and retention of knowledge.

I like used books with notes in it. It's interesting to see what someone previously reading felt was important or to glimpse into the past life of book itself.

This made me remember a time I checked a book out from the library and found lots of little notes written in Chinese characters in the margins throughout the book. Most if not all were, I assume, translations of words. It was quite nice - they had wonderful penmanship.

I keep my own notebooks for my own notes. I don’t need to scribble all over a book and ruin it for the next reader.

I would ask how it ruins it for the next reader. I suppose it depends on the definition of "scribble", but notes in the margins and underlined words are helpful for me when I'm scribbling as it helps me regain the context. Practically, when I borrow/lend a book, I find it interesting on their thoughts, as opposed to bothersome.

It’s distracting and messy.

I’m not reading a book for half-baked insights scribbled in the margins by past readers unknown.

Yes, I understand. I disagree with scribbling in your own books because (I found) scribblers often forget and do it in the books I lend them. Also, I inherited books from my aunt, who was a heavy scribbler, and it annoys me. It has a factor of having a connection to her, which I appreciate... but I also find her scribblings distracting.

Plus "your own books" are never truly just your own. In the example from the author of TFA, they are his family's. I wouldn't have wanted my brother's or parent's scribblings in books from our family bookshelves!

buy a 500 pack of bookmarks on amazon and sprinkle them around at all your reading spots, all of my books get their own bookmark

I usually get a free bookmark with every book I buy, but soon misplace them. Bending pages is the one sin I allow myself without much guilt. The damage is very light anyway.

I bend pages not just to keep my current spot, but as persistent markers to things I want to find later, notes I've scribbled, or whatever. A big ephemeral dog ear for current location, and then a bunch of tiny little persistent dog ears for reference.

Index cards are the way. Bonus: notes.

> I also accept bending pages to remember where you left the story; I never have bookmarks handy.

I decided about 20 years ago I wasn't going to use bookmarks anymore. If I can't find where I was, I need to reread from whatever I recognize. If I can't figure out a place to drop in and understand what's going on, I should just start over from the beginning (it'll probably be faster the second time anyway.) I also really hate dogears; they crack off in about 10 years or so.