How to Understand and Remember What You Read: 4 Questions to Ask While Reading a Book
Let’s be honest, reading is the closest things we humans have to a superpower.
And yet, even when we somehow, miraculously carve out time to read something, it can be very difficult to understand and remember what we read – especially if it’s a difficult book that’s worth reading in the first place!
This is because, as Mortimer Adler and Charles Van Doren note in their perennial classic How to Read a Book (affiliate link), we aren’t usually taught how to become skillful readers. Instead, in school, we’re given the bare basics and then set loose into a jungle of long and complicated books that we struggle to make sense of.
So far, How to Read a Book is the most helpful guide I’ve found to become a better reader – to getting better at understanding and remembering what I’ve read.
As a Ph.D. student who spends most of his time around books, I need to become the best possible reader I can be! However, I believe that everyone can benefit from How to Read a Book, so here’s a distilled summary – a guide you can use while reading any book.
(Note: for the sake of remembering what you’ve read, I highly suggest that you take notes as you answer these questions! You can use a good old piece of paper, or something digital, like Evernote.)
When Reading a Book (Or Anything, Really), Ask These Four Questions:

What's this book about, as a whole? (Summarize It)

What's this book about, in detail? (Outline It)

Is this book true? (Critique It)

So What? (Use It!)
1. What is this book about, as a whole? (Summarize It)
Try to read in such a way that, if someone stopped you and asked you for a 13 sentence summary, you could give it to them.
Sounds easy enough, right? But it’s harder than it sounds. After all, how are you supposed to fit an entire book into a couple sentences?!
To help, try and answer the following subquestions before/as you attempt to summarize the book.
What kind of book is it?
Is it fiction? Nonfiction?
If it’s nonfiction, is it practical (teaching how to do something) or theoretical (teaching you information)?
What's the book's topic or subject matter?
Are you reading a book about astronomy? Frogs? How to build a birdhouse?
What problem(s) is the author trying to solve?
Why did the author write the book? What problem is the author trying to solve? What question is the author attempting to answer?
(For practice, in case you couldn’t tell, I’m writing this blog post to help you understand and remember what you read!)
2. What is this book about, in detail? (Outline It)
Understanding a book in its entirety is very important, but we can’t forget about the parts that comprise the whole!
As you read along, try to outline the main points and subpoints of a book. For many nonfiction books, this can be done based on the table of contents.
In addition to outlining the book, the following questions are worth answering at this stage.
What are the key terms in the book?
Keep a list of important or new terms that you encounter as you read, as well as the author’s definitions of these key terms.
What are the key sentences, propositions, and arguments in the book?
What is the author trying to say? What is the author claiming or proposing? What point is the author trying to make?
What solutions does the author offer to the problem(s) they are trying to solve?
Here we start to move from interpretation to evaluation. Did the author solve the problems they were trying to solve?
If so, great! How? What’s the solution?
If not, then that’s your first avenue for critique. But here’s another thing to consider/note: Does the author realize that they haven’t solved the problem(s)?
3. Is this book true? (Critique It)
After understanding a book, the next thing to do is critique it. I mean this in the sense of “evaluate” the book, of course, not just naggingly criticize it!
First, make sure that you’ve understood the book. Then, make sure to give reasons for your evaluations. Don’t critique a book that you don’t understand, and don’t merely state personal opinions without backing them up somehow.
OK, here are the questions you should answer at this stage.

(Where) Is the author uninformed?

(Where) Is the author misinformed?

(Where) Is the author illogical?

(Where) Is the author's account incomplete?
As Adler and Van Doren note (on page 164 of my 1972 edition), in order to disagree with a book, you should be able to show how the author is uninformed, misinformed, or illogical.
If you can’t show that, then, in some sense, you have to agree with the author. However, “you may suspend judgment on the whole, in the light of the last point” regarding the author’s incompleteness.
4. So What? (Use It!)
OK, you’ve read the book, summarized it, outlined it, and critiqued it.
Now what?
Has the book challenged your assumptions in any way(s)? Do you need to change your views?
Has the book raised any questions for further research/learning? Do you need to find another book and start the process all over again?
So, to summarize:

What's this book about, as a whole? (Summarize It)
 What kind of book is it?
 What is the bok's topic or subject matter?
 Can you summarize the book in a sentence or two?
 What problem(s) is the author trying to solve?

What's this book about, in detail? (Outline It)
 Can you outline the book?
 What are the key terms in the book and what do they mean?
 What are the book's main sentences/propositions/arguments?
 What solutions does the author offer?
 Has the author solved the problem(s)? Do they realize they've (not) solved it?

Is this book true? (Critique It)
 What problems has the author failed to solve?
 (Where) Is the author uninformed?
 (Where) Is the author misinformed?
 (Where) Is the author illogical?
 (Where) Is the author's account incomplete?

So What? (Use It!)
 Has the book challenged your assumptions?
 Has the book raised questions for further research?
I hope these questions give you a good starting point. As I said earlier, How to Read a Book is the best book I know of on this topic. If you’d like to dig deeper and become a better reader, I highly recommend that you buy a copy!