TLDR – I think the value of reading a book once (without active engagement) is awkwardly small, and the value of big time investments like reading a book several times – or actively engaging with even part of it – is awkwardly large compared to that.
Karnofsky, H. (2021, October 20). Reading books vs. Engaging with them. Cold Takes. https://www.cold-takes.com/reading-books-vs-engaging-with-them/
In this short post, Holden Karnofsky suggests that the cost/benefit ratio of how we typically think of reading may not be as simple as we intuitively expect i.e. you probably think that ‘more time spent reading’ = ‘more understanding and retention’.
However, Karnofsky points out that, if you’re simply reading to inform yourself about a topic (non-fiction, general audience), it may be worth reading a couple of book reviews, and listening to an interview or two (about 2-3 hours in total), rather than invest the significant amount of time necessary to really engage with the book (about 15-50 hours).
A few hours of skimming and reviews/interviews may get you to 25% understanding and retention, which in many cases may be more than enough for your needs of being basically informed on the topic. Compared to the 50 – 100 hours of analytical engagement with the text, which would only get you to 50% understanding and retention, this seems like a good return on investment.
That being said, if your goal is to develop expertise, both Karnofsky and Adler (‘How to read a book’) suggest that you need a deep engagement with multiple texts.
Obviously, the number of hours and percentage of understanding and retention are broad guesses, although I found the basic premise compelling and relatively well-aligned with my own experiences. In the past couple of years I can think of at least 2 books where I’ve spent 2-3 hours listening to author interviews and reading a couple of book summaries and reviews, that have got me to a pretty decent understanding of the main premise of the book. Without spending the 10-15 hours it would have usually taken me to read them.
Note: I recognise that this may be an unpopular suggestion.