People flinch at this. Writing in a book feels like damage, and for a rare or borrowed one it is. For an ordinary paperback that you own, it is the difference between reading and thinking.

My copies are a mess. Underlining, marginal question marks, the occasional flat 'no'. Dates, sometimes, when the sentence landed on a day that made it land harder. A system that developed without design and would be illegible to anyone else.

The value shows up on re-reading. A book you have marked up is a record of who you were the last time through. I reread something this spring that I had annotated in 2019 and spent as much time arguing with my own marginal notes as with the text. Two of them were embarrassing. One was better than anything I had thought about the book since. That is not an experience a clean copy offers.

Second-hand books carry the same thing from a stranger. I have a 1974 paperback picked up in Sheffield with a previous owner's notes running the whole way through — careful, pencil, in a tidy hand, and increasingly annoyed with the author from about chapter four. Near the end they wrote a single line across the bottom of a page that reframed the whole book for me.

I have no idea who they were. It was a better piece of criticism than most of what I have read about that book in print, and it reached exactly one person, decades later, by accident.

The digital equivalent exists and is not the same. Highlights sync, and I have thousands of them, and I have never once gone back to read them. They are in a list, detached from the page, out of position. The marginal note works because it is next to the thing, in your handwriting, at the moment of the reaction. Strip out the position and the immediacy and what's left is a quote you saved.