It was a fine book, but this summary serves the point perfectly while also being way shorter. My working assumption with all these popular books is they could be half (or less) as long and retain effectiveness.
I’ve read a lot of book abstracts (from getabstract.com) of business or pop science books in about 6 to 20 pages. They really do seem to contain all the pertinent points, but in my experience you read them, nod your head (“that makes sense”), and then the next day have forgotten all about it. Zero retention.
A book, by contrast, is much longer and, yes, repetitive, but also gives context, examples, applications, anecdotes, etc., and in my experience all this seemingly superfluous stuff helps with retention.
But they could probably be, say, 75 pages rather than 250. The problem is that the economics and practices of the publishing industry--and, in all fairness, the expectations of most book buyers--are built around 250-300 page books. So authors end up padding out their 75 page book to 250+ pages.
Philip Greenspun wrote the following in 2003. It was in the context of blogs as an alternative but the reality is that books still carry a certain gravitas that online publishing usually doesn't have.
"Let’s go back to the beginning. The commercial publishing world supports basically two lengths of manuscript: the five-page magazine article, serving as filler among the ads; the 200+-page book. If you had a 20-page idea and didn’t have access to the handful of “long-copy” magazines in the U.S. (old New Yorker, Atlantic, etc.), you could cut it down to a meaningless 5-page magazine piece or add 180 pages of filler until it reached the minimize size to fit into the book distribution system (cf. any diet book or business bestseller)."
I find it works less well when you're just hoovering up a bunch of random content that was perhaps interesting relative to current events and trends but is less so in isolation. Nothing wrong with doing it as a way of archiving past work but it's probably not something that's likely be to the average reader.