On rereading
The second pass is never the same as the first, and the gap between them is the only honest record I keep.

I have read Housekeeping four times, and I could not tell you what happens in it.
That is not quite true. I could give you the shape — a house, a lake, two sisters, a train that goes into the water and does not come out. What I could not give you is the thing I would have given you at twenty, which was a confident account of what the book was about. That account existed once. I remember having it. I could not reconstruct it now under oath.
The first pass is a kind of weather
The first time through a book you are mostly finding out whether you can stay in it. The prose is unfamiliar, the names have not settled, and a good deal of attention goes to the mechanical work of holding a cast in your head. What you come away with is less a reading than a climate — a sense of whether the thing was cold or warm, generous or withholding, whether you were welcome.
This is why first impressions of books are so unreliable and so strongly held. You have a real experience and almost no evidence. The confidence comes from the vividness of the weather, not from anything you could point at on the page.
What changes on the second pass
The second time, the plot stops being a task. You know the train goes in the lake. That frees up an enormous amount of the attention that was previously spent on bookkeeping, and it gets spent instead on sentences.
I do not think this makes you a better reader of the book. I think it makes you a reader of a different book. The first one — the one where you did not know about the train — is genuinely gone, and it was not a worse book. It was a book with suspense in it. You cannot get that back, and pretending the informed reading is simply the correct one is a way of not noticing the loss.
The gap is the measurement
Here is the part I keep coming back to.
If you reread something at long intervals — five years, ten — the book holds still and you do not. Everything that has changed shows up as a difference in what you notice. The passage that seemed like scene-setting turns out to be the argument. The character you found tiresome turns out to have been the only honest one. Nothing on the page moved.
So the difference is a measurement, and the instrument is the text. This is the only reason I keep a reading log, and the reason it is almost useless as a list of books — what I actually want from it is the annotation, five years old, that I now disagree with. That disagreement is data about me that I could not have collected any other way, because I would not have known to look.
Against the completist reflex
The counter-argument is obvious: there are more books than time, and rereading spends a finite resource on something already consumed.
I think that argument smuggles in an assumption about what reading is for. If the point is coverage — to have read the things — then yes, rereading is waste. But nobody who says this actually behaves as though coverage were the point. They do not read summaries. They do not accept a friend’s account as a substitute. They want the experience, which means they already believe the experience is the thing and not the information.
And if the experience is the thing, then a book that produces a different experience on the fourth pass is not a book you have finished. It is a book that keeps working.
I still could not tell you what happens in Housekeeping. I could tell you, fairly precisely, what has happened to me.