On skimming books
There is a commonplace but misguided idea that reading a book means reading it from cover to cover. As with many binary assertions, this doesn't hold up even to the lightest analysis. What if you skip a word? A less important paragraph? What if you nod off during a whole chapter, but still get enough of its content to be able to read the rest of the text without major issues?
And what about the quality of reading? In some (non-fiction) books, the most important content is in the first (say) 80% of the book, with the last 20% having chapters that are of a more complementary nature. Let's say I read the whole thing, and I do it very fast. You, on the other hand, read it very carefully, making pauses to think, taking notes, reading more actively overall. But you don't read the last 20%. Would it make sense to say that I read the book and you didn't, or even that I read "more" of it?
My guess is that this all-or-nothing mentality comes from a related belief: the idea that reading more books is better. This is clearly nonsense, but I think most of us believe it at some level (I know I'm not completely immune to that impulse).
Reading challenges are, at least in part, a result of these twin ideas of a binary definition of "having read" plus the notion that reading more is better.
Another effect of this mindset is the—in my experience—popular notion that re-reading is a waste of time. I've heard more than one person proudly making the following argument: the only reason to keep a book you have already read is to re-read it, and re-reading is useless, ergo there's no point in keeping books. Both premises are obviously wrong, but they, and the whole syllogism, seem to ring true to a lot of people.
Yet another consequence of these ideas is the resistance to abandon a book: if you start a book and don't finish it, you've failed. You invested some time on it and now you can't even claim you've read it! You better grind on and finish it even if you hate it.
(There is a perhaps valid reason to force yourself to finish books, which is to develop some kind of reading discipline because you want to spend more time reading. I guess this is fair, even if I think there are much more effective ways to accomplish that than self-punishment. But I don't have anything against wanting to read more; my problem is with wanting to increase an arbitrary number using a silly definition.)
All of this is a long preface to talk about something I love doing: skimming books. By this I mean picking up a book and reading enough of it to form an initial idea of what it's about, how good it is, how much effort would it take to read it, and so on.
In a way this is a normal practice: it's what you do in a bookstore when you grab a book and, well, skim it. The main difference is that I'm somewhat systematic about it.
It works like this: I keep a list of "To check" books, with titles that someone recommended to me, or that I saw mentioned somewhere and thought they seemed interesting. Now and then I choose some book from that list, skim it, write some notes about my impressions, and remove it from the list. (I use Obsidian for both the list and the notes.)
This might sound like a chore, but I enjoy it so much that I'd do it just for the fun of it. But I also think it's very useful, because I build a better backlog of things I want to read. Many times it happens that I find something that looks very interesting, but that, for any reason, it's not the right time to read it. Some time later—maybe more than a year later—I pick it up at the perfect moment and I confirm I did the right thing.
This kind of reading is, of course, not original at all. The classic How to read a book has a whole chapter on what they call "Inspectional reading", of which skimming is a possible application. A paragraph from that chapter perfectly summarizes it:
Giving a book this kind of quick once-over is a threshing process that helps you to separate the chaff from the real kernels of nourishment. You may discover that what you get from skimming is all the book is worth to you for the time being. It may never be worth more. But you will know at least what the author's main contention is, as well as what kind of book he has written, so the time you have spent looking through the book will not have been wasted.