If a book's ideas can be absorbed in 15 minutes, was it ever really a book?

I've seen these business summaries on offer elsewhere--it always struck me as an approach to signaling, not learning. In this model the "reader" can manufacture the appearance of knowledge of a subject without taking the time to invest oneself in it. Or perhaps now the books even manufacture the appearance of knowledge while being tiny ideas unworthy of serious consideration.

I think if I was working with anyone who used a service like this though, I would have second thoughts about them. Isn't this just trend-chasing dressed up as knowledge acquisition?