It is my little secret & I had quite a big internal argument about whether I should post this or not but I know this will help a lot of people here so let me show you how to do it in short...
1- Go to kindle.amazon.com
2- Put in any keyword on the search box...lets say - self improvement.
3- The first result is a book called - The Secret Art of Self-Development: 16 little-known rules for eternal happiness & freedom
4- Scroll down on that page and look for "Highlights".
6- And bam...you have key highlights from that book. In other words - People are telling you what they found useful and have pointed that out for you.
The best part is - That you will get the most high quality usable ideas for writing articles, making courses and doing overall research. Trust me, try it with any keyword right now and you will see how powerful this truly is.
I hope this helps some of you...