Marginalia: how to take notes in books you will reread

A margin note is worth keeping when it argues with the text. Summaries are already in the book; objections, counter-examples and connections are not. The format that survives a year is three lines: the page, the sentence that provoked you, and what you thought about it.

What is marginalia?

Marginalia are the notes readers write in the margins of a book — Coleridge's word, and he wrote enough of them that friends lent him books specifically to get them back annotated. The tradition matters here because it sets the standard: the notes people still read two centuries later are arguments, not abstracts.

Digital or on paper makes no difference to the rule. What changes is only whether the note is attached to a page number you can find again.

Why not just highlight?

Because highlighting records that something felt important, and nothing else.

Come back a year later to a page of yellow and you will not know whether you agreed, disagreed, or simply liked the phrasing. Highlighting is a bookmark for an emotion. It costs almost nothing at the time, which is precisely why it produces almost nothing later.

If you highlight, treat it as a shortlist to write notes from at the end of a session, not as the note itself.

What does a useful note look like?

Three lines, in this order:

• The page. Without it the note is unverifiable and you will not go back.
• The sentence. Quote it, short. Not your paraphrase — the author's words, so a year from now you can tell what they actually claimed.
• The reaction. The part with the value. "Doesn't this contradict ch.3?", "same as the Ops incident in March", "true for teams over 20, not under."

The reaction line is the one people skip, and it is the only one that could not be reconstructed from the book itself.

How many notes per book?

Fewer than you think. Somewhere between five and fifteen for a normal non-fiction book.

Fifty notes means you were transcribing, and a transcription is a slower copy of a thing you already own. The discipline of a small number forces the question "is this actually worth writing down?", and that question is most of the value of taking notes at all.

When should you write them?

At the moment of the reaction, not at the end of the chapter. The objection you had on page 96 is gone by page 120 — you will remember that you disagreed, not what about.

If stopping to write breaks your reading, mark the page and write at the end of the session, but write the same night. Notes deferred to the weekend do not exist.

Should notes be shared?

Inside a group, yes; publicly, no.

Shared notes inside a team reading group are the best part of it — seeing that someone else stopped at the same sentence for the opposite reason is exactly the disagreement the group exists to produce. It also means the person at page 40 can see what is coming without a meeting.

Public is different. The moment a half-formed objection might be quoted outside the room, people stop writing half-formed objections, and half-formed objections are what marginalia are made of. This is why in Marginalia a published book page shows the title, the author and the progress — and never the notes. Sharing a book and sharing what you wrote in it are not the same permission, and only the first one is offered.

Do notes make a reread worth it?

They are most of what makes a reread worth it. A second pass through a clean book is a slower version of the first pass. A second pass through a book you argued with is a conversation with a slightly younger, slightly worse-informed version of yourself, and you will find you were wrong often enough to make it interesting.

That is also the honest test for whether a book deserves a note at all: would you want to reread this? If not, quit it and save the ink.

The short version

• Argue, do not summarise.
• Page, quoted sentence, reaction — in that order.
• Five to fifteen notes per book, not fifty.
• Write on the night, not at the weekend.
• Share notes inside the group; never publish them.