Most nonfiction books should've been 1000-word articles.
I find myself abandoning a lot of books right around the 25-30% mark.
Not because they're bad, but because I fully get the gist by that point and it's right around when the repetition of examples and ideas begins.
I'm okay with abandoning a book midway now. Just a couple years ago, I would power through the whole thing in fear of missing out on some crucial ideas in the later chapters.
Now, I just have fun with it. If it piques my interest, great – I'll buy it, read the chapters that seem interesting, get what I came for and move onto the next one.
I think a lot of these authors are just trying to meet some sort of quota. I dunno.
There's elegance in brevity.