Or the much earlier Pale Fire.
OP, don’t read any of the “Complete Idiot’s Guide” or “__ for Dummies” books. They are full to the brim with the blurbs you hate.
The thing to bear in mind is that, back in the 19th Century (and even the early 20th Century) most people really didn’t have much else in their homes to do entertainment-wise (No TV or even radio until the late 1920s), so details were important to the sort of people who liked to read books about the sort of stuff Wells and Verne and Conan-Doyle and Haggard et al were writing about. They’re still important to some readers (such as myself!) even nowadays.
As for “Sidebars” in non-fiction books; I’m very fond of them. They’re useful “asides” IMHO. And if you’re having trouble working out how to read them, the advice I give people is this: Read the “Main” (ie non-Sidebar) text first, then the Sidebars.
Every writer and book designer I know spends a lot of time thinking about exactly where sidebars should be placed. If we wanted them at the end of a chapter we would put them at the end of a chapter. If they make just as much sense not being read until the end of the text, then you shouldn’t have them in the first place, is my advice.
My background experience here is in newspaper and magazine layout, and when I’m laying out a page, the Sidebars are always for exactly that- “Asides”, information that’s useful and interesting, but not the primary focus of the piece.
In at least one case, Verne did – it’s in Around the Moon, the sequel (actually the essential second half of ) From the Earth to the Moon. Typically, it frequently gets reprinted incorrectly.
Sometimes the equation actually is both important and relevant to a story. Fred Hoyle’s the Black Cloud includes one such example, and it shows how the character frames a question in his mind and develops it.
For my part, I love these technical digressions. I’m an avid Verne fan (and wells fan), and actively seek out his books. I loved all the technical stuff in Moby Dick. Abridgement, to my way of thinking, ruins that book.
But sometimes you pretty much have to read the sidebar at the end. Or figure out for yourself where to interrupt the main text. If the main text just keeps going and the sidebar is above or off to the side but there’s no clear moment of when you stop reading the main text…then what do you do?
If my memory serves, one book that handled the side bar issue well was the South Beach Diet book. Any diet book has to include success stories, so what the author did was include a success story at the end of each chapter. That way, the “side bar information” was worked into the text at a nice break point.
My wife and I, being imperfect beings and all that, like sidebars as well. While I have no problems with blocks of text, I like the added details that a well-placed and written sidebar can bring to a book.
If it’s a footnote, likely when I come upon it or at the end of the paragraph (in my mind, I read the footnote like a parenthetical phrase - it’s actually a different voice in my head).
If it’s a sidebar, then I read it sometime in the middle of the work, pretty much where the sidebar is placed. Again, it’s a different voice than the one that I hear in the main passage.
If I get to a sidebar I read it. There may be times when I finish the paragraph on the next page and then turn back, but most of the time I read it whenever I get to it, or when it’s referred to in the text.
Seriously, how else would you do it? Why would you do it otherwise? How would it take you out of the narrative so badly that you couldn’t follow it? How do you pick up the thread again when you put a book down? The narrative changes from paragraph to paragraph no matter what. Adding a sidebar shouldn’t damage that.
I don’t remember a discussion about the difficulties of sidebars for readers before, so these questions are a serious request for information.