Big Brain Ideas

How to Read a Book, Chapter 7: X-Raying a Book

A common theme in How to Read a Book is understanding what a book is about. Adler continues building on this theme in X-Raying a Book by suggesting that we summarize the book we’re reading as briefly as possible and write our own outline for the book. Adler’s argument is that these tasks demonstrate your understanding of the logical structure of the book, which is a prerequisite for the reading skills that come later in How to Read a Book.


Logical Structure vs. Physical Structure

I’ll refer to a book’s logical or physical structure several times in this post, so I thought it would be a good idea to make sure we’re on the same page about what that means.

A book’s physical structure is the parts, chapters, and chapter sections. Each piece of a books physical structure usually begins with a title and can be found in the table of contents (although chapter sections may not be listed).

A book’s logical structure is the set of common themes, key ideas, arguments, and supporting evidence that makes up the entire book. Often the logical structure closely follows the physical structure, but not always. Sometimes an argument begins in one chapter and is finished in another. Sometimes a common theme is brought up in seemingly random places throughout the book.

In the same way that a book’s physical structure is hierarchical — parts have chapters and chapters have sections — so too is a book’s logical structure. Common themes are made up of a set of key ideas. Each key idea is made up of a set of arguments, and each argument is backed up by one or more pieces of supporting evidence.

Key Ideas

Summarize the Work

If you understand what you’re reading, you should summarize it in a few sentences. As an approximation, the more comfortable you find this task, the better your understanding of the book.

Our goal is to understand the logical structure of the book. What arguments is the author making? How are these arguments compiled into a set of key ideas? Adler talks about finding the “unity,” the single thread of plot that permeates the entire work. This is what we want to identify and describe in our summary.

Another exercise you can try is summarizing the work at the different levels of hierarchy. What is the book about as a whole? What is each common theme about? What is each key idea about?

Outline the Work

You may be able to guess the logical structure of a book, but that doesn’t mean you understand it. When you guess, you make assumptions, and assumptions often turn out to be wrong. By explicitly outlining the book, you remove those assumptions and focus on what the author is saying instead of what you think the author is saying.

One way to outline a book looks like this:

Repeat this structure for each common theme.

Outlining is immensely time-consuming, so the amount of detail in the outline should be proportional to the book’s importance and the value you expect to get from it. If a book is more important or you think a more detailed outline will yield more value, then go for it. If the work is less important or a simple outline will get you most of the value, then keep it simple.

Outlining naturally captures the different levels of hierarchy in a book, so no additional exercise is needed on that front.


I thought this chapter was great and full of fantastic advice.

Here’s what I’m taking away:

I’m always looking for second opinions on what I read. If you’ve got an alternative perspective, you can find me on the Twitter.

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