Let’s say you’re interested in a 500-page serious nonfiction book, and you’re trying to decide whether to read it. I think most people imagine their choice something like this:

I see things more like this:

I’m guessing these numbers are pretty weird-seeming, so here are some explanations:

• Just read the title (and the 1-2 sentences people usually say to introduce the book): "seconds" of time investment, 10% understanding/retention. 10% probably sounds like a lot for a few seconds of thought! I think this works because the author has really sweated over how to make the title and elevator pitch capture as much as possible of what they’re saying. So if all I want is the "general gist," I don't think I need to read the book at all.
• Skimming or reading the book: hours of time investment, only 12-15% understanding/retention. This is based on my own sense of how much I retain when I "simply read" the book (and don't engage much with critiques of it, don't write about it, etc.) - and my perhaps unfair impressions of how much others seem to retain when they do this. If person A says they've read a book and person B says they haven't but they've heard people talking about it, I often don't find that person A seems to know any more about the book than person B.
• Read reviews/discussions of the book (ideally including author replies), but not the book: 2 hours of time investment, 25% understanding/retention. Good reviewers know the context/field for the book better than I do, and probably read the book more carefully than I did. Hopefully they picked out the really key good and bad parts, and if those are the only parts I retain, that’s probably more than I could hope for with just a slow reading.
• Read the book slowly 3 times, with 3 years in between each time: 48 hours of time investment, 33% understanding/retention. This implies that the 2nd and 3rd readings are actually more educational than the 1st: the first only gets me from 10% (which I got from reading the title) to 15%, the next two bring me to 33%. I think that’s right - it’s hard to notice the important parts before I have the whole arc of the argument and have sat with it. Hearing other people talk about it and seeing some random observations related to it also help.
• Write my own thorough review of a particular debate between the book's critics and its author: 16 hours of time investment, 33% understanding/retention. (The table has more detail on what this involves.) This is the same time investment as reading the book slowly, and I'm saying that is worth something like 5x as much (since once I've read the title, reading the book slowly only takes me from 10% to 15% understanding/comprehension, whereas this activity takes me from 10% to 33% understanding/comprehension).
• Write my own summary of each of the book’s key points, what the best counterargument is, where I ultimately come down and why: 50-100 hours of time investment, 50% understanding/comprehension. I know hugely more about the books I've done this with than the books I haven't. But even here I'm only estimating 50% understanding/comprehension. I don’t think it is really possible to understand more than 50% of a serious book without e.g. spending a lot of independent time in the field.

TLDR - I think the value of reading a book once (without active engagement) is awkwardly small, and the value of big time investments like reading a book several times - or actively engaging with even part of it - is awkwardly large compared to that.

Also, the maximum amount of understanding you can get is awkwardly small.

And a lot of the best options get you a “raw deal” on sounding educated:

• If you read reviews and not the book, someone else can say they read the book and you can’t, even though you spent just as much time and retained more of the book.
• If you digest the heck out of the book, you still can’t say anything in casual conversation except “I read the book,” which is also what someone can say who spent way less time and retained WAY less.

Ultimately, if you live in the headspace I’m laying out, you’re going to read a lot fewer books than you would otherwise, and you’ll probably be embarrassed of how few books you read. (But if more people described their engagement with a book in detail instead of using the binary “I read X,” maybe that would change.)

Edited to add clarification: this piece is about trying to casually inform oneself in areas one isn't an expert in, via reading books (and often other pieces) directed at a general audience. A reader pointed out that when you have a lot of existing expertise, the situation looks quite different, and often skimming or reading is the best thing to do. (Although in this case I would add that one is probably mostly reading reports, academic papers, notes from colleagues, etc. rather than books).

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