In most books, the important ideas and insights are usually unevenly distributed across the whole book. Which means, if your intention behind reading books is just to gain knowledge (and not care about its entertainment value) then there’s always some part of the book which doesn’t add as much value. Does it mean one should read just the book summaries? Scott Young, makes a case in favor of reading the whole book instead of books summaries. And his argument is quite convincing.
…the value of books comes not only from their ideas, which of course can often be gleaned from a summary, but from being a difficult mental task that requires focus and simultaneously guides deeper thinking…reading a hard book is more than just the ideas you obtain from it. Thinking about the book’s content while you read it is what matters. So a really long, good book on a topic will provoke much longer reflection and therefore have a much larger impact than a short summary or perhaps even many short summaries.