If you asked me, I will tell you that book summaries are a great failure, but I personally use them it, seems controversial right? I'll tell you how!
I consume so much content every day, including book summaries, because they're only beneficial if you hear a lot of them, either daily (gives you 365 summary per year) or more than once today which will obviously add up to more than this.
The 300 pages book, couldn't be compressed into a 12min summary that is not more than 5 pages, what a summary does is that it gets the most important 2-5 points that the author talked about and discuss them, that's why I said its a failure, but what if you get 3 points from every single book and you hear 2 of them daily (24mins out 24 hours) which gives you 2190 points discussed every single year, wouldn't this add up to your life? surely it will.
Also, another thing that is soo important, is that if you don't write these points, then you almost had nothing as a benefit, because you'll forget all of them, the only solution is to write what you've learned through the summary from your own point of view, like what you've concluded not what you have heard.
and if you did this, you wrote notes twice per day for the 2 summaries you've heard, then you'll have so much information and you'll get so much from these great books made by the greatest authors, and maybe it could be even more efficient than reading 20 books a year (because of diversity).