Often the point of a non-fiction book is to spend hours thinking deeply about the book's subject. You could probably get the major ideas in the length of a short blog post. But that's spending 10 minutes thinking about the topic as opposed to 2-3 hours.
You can think of it as the difference between reading about a subject online and having a long conversation about that subject with friends. For me personally, the length and guided interaction of a book makes a difference
Definitely. Few years ago I subscribed to this service called "Blinkist" which summarizes whole books into several pages.
But soon enough I understood it's pointless. I got superficial understanding of the books from the summary, but I forgot it just as quickly. If you want to extract value from a book, you must give it time, you must think about it, go deep, try different associations etc.
You can think of it as the difference between reading about a subject online and having a long conversation about that subject with friends. For me personally, the length and guided interaction of a book makes a difference