I start a lot of books. I finish maybe a third of them. For years this bothered me in a low-level way — a shelf of half-read things felt like evidence of some character flaw.

I've changed my mind, and the argument that changed it is about cost.

The sunk cost is the whole thing

You pick up a book. A hundred pages in, it's not working. The argument is thin, or the prose is a slog, or you've already got the idea and the remaining two hundred pages are examples of it.

The instinct is: I've invested a hundred pages, I should finish.

But the hundred pages are gone either way. The only live question is what the next three hundred are worth compared to the first hundred of something else. Framed that way, finishing out of duty is just paying twice.

The finishing instinct is sunk cost wearing the costume of discipline.

What changed in practice

I keep a shelf — physical, visible — of books I stopped. Not hidden. Stopping isn't failure so it doesn't get hidden.

Some get picked back up. That's the surprise, actually. Three or four have been books I wasn't ready for rather than books that were bad, and coming back a year later they opened straight up. If I'd forced through the first time I'd have extracted nothing and concluded the book was poor.

The part I'm still unsure about

There's a kind of book that's genuinely hard in the early going and pays off precisely because you pushed. Difficulty isn't always a signal to stop. Sometimes it's the thing you came for.

I don't have a clean rule for telling those apart. My rough test: am I bored, or am I struggling? Boredom means the book has nothing more for me. Struggle means it has something I don't have yet.

Boredom, I put it down. Struggle, I keep going. I get it wrong both ways regularly.