How to Annotate Nonfiction Books

How to Annotate a Nonfiction Book

To annotate a nonfiction book, mark its argument rather than its best sentences. Give each part of the argument its own mark:

Where a novel gets annotated for its language and moments, you mark a nonfiction book for its structure. Two additional blank pages complete the system: one describes the book in one sentence, and the other has an index of the passages you'll want to read again. For the basics (what to mark with, and how to do it without ruining the book), start with How to Annotate Books.

Map the Argument First

Most nonfiction gives you its structure up front. The introduction states the thesis, the table of contents lists the parts, and each chapter opening says what the chapter will show. Read those first, then mark the book against them.

Write a T in the margin where the author states the thesis in full. Then number each main point in the margin as it comes up. Mortimer Adler suggested these margin numbers in his 1941 essay "How to Mark a Book", to track "the sequence of points the author makes". Months later, flipping through the numbers shows you the skeleton of the argument instead of pages of highlights.

Some books don't follow this structure. They repeat themselves, or the argument comes together slowly across many chapters. In that case, write your own one-sentence thesis on the front blank page early on and mark against it (you can fix the sentence as you go). Dense books need this the most.

I came across Adler's method through Farnam Street's summary of his best-known book:

How to Read a Book

by Mortimer J. Adler and Charles Van Doren

The classic guide to reading actively: say what a book is about in one sentence, outline its parts, find the argument, then judge it.

Est. read: 7h 48 min

Get your reading estimate

Mark Claims and Evidence Differently

A claim is what the author wants you to believe. Evidence is what they offer for it: a study or data set, for example. Don't mark both the same way, or you'll lose how well supported each idea is.

Underline claims, draw a vertical bar in the margin next to the evidence, and circle an S beside any study or statistic worth checking. On a flip-through later on, an underline with no bar beside it is a claim the book never backed up. A circled S is a source to look up before you repeat the claim to anyone.

In an ebook, highlight the evidence in a second color. (I used to give every color a meaning. Now I use one color and put the meaning in a note.)

Keep the Author's Turns Separate From Your Own

A turn is where the author acknowledges a point, changes course, admits a limit, or narrows the claim. Turns are rarely the quotable lines, but they show where the argument is weakest. Mark them with a ! in the margin.

Your own reactions need their own mark. A margin note like "not always" could be the author's caveat or your objection, and over time you may not be able to tell them apart. On paper, put your own words in brackets. In an ebook, the app separates them for you: the highlight is the author's, the note is yours. My notes say how I'd use an idea (apply it myself), or why I disagree with it.

Writing down an objection makes you read more carefully, because you have to think it through to phrase it. Often enough, the author answers it a few pages later.

Outline in the Front, Index in the Back

In "How to Mark a Book", Adler used the blank pages at the back to collect the author's points and the ones at the front for his own outline of the book.

The back page is your index. When a passage is worth coming back to, add a short tag in your own words and the page number:

• default effect – 34
• study to check (n = 40) – 112
• [disagree] willpower – 187

Try not to cram too many entries in your index, or it becomes too long to scan. Five to fifteen entries are plenty.

The front page is your outline: the book in one sentence, with its main points numbered to match your margins. Finish it when you finish the book. Adler called his outline the measure of his understanding. If you can't fill the front page, you probably didn't fully get the argument yet.

In an ebook, the app's list of highlights and notes is your index. Start each note with its tag so the list reads like an index, and keep the outline in a note on the first page or in your notes app.

Annotating Textbooks, History, and Other Nonfiction

The marks stay the same, but what you mark more and less of changes:

Revisit When You Need It

You don't need a revisit schedule. The marks are for the day a question comes up: someone asks about the book, you want to apply an idea, or you start another book on the same topic.

Open the front page first, then the index, and follow only the entries that answer your question. With numbered points and a short index, that takes minutes instead of a full reread.

Move what still matters into a note outside the book, so it doesn't stay locked in one physical copy or one app. A reading journal is a good home for it, and these book journaling prompts help you start yours. For the extended retention system, see How to Actually Absorb What You Read.

A book that isn't paying off doesn't need any of this. If marking every claim turns nonfiction into homework, mark less (How to Read More Nonfiction explains why that's fine). Otherwise, start with the two blank pages in the next nonfiction book you open.