Self-improvement books are great for improving yourself. They contain years of knowledge and hard work compressed into an easily digestible format.
However, the problem with such books is that the ideologies stated in the book are easy to forget once you get out of touch with it.
Now, what's the use of investing your time and reading a whole book if you can't put the knowledge to use?
However, there's one simple solution to this problem. It's called taking notes.
Whenever I read a self-improvement book, I take notes as I go through each chapter.
I use Trello boards to make my notes for each book but you can use a plain notebook or whatever suits you.
Just extract the key points from each chapter and make a note of it in your own words. When you need to revisit the points, it'll be as easy as scanning through some 1-2 liners.
Try it out. It helps. This is how you can make the most of every non-fiction book you read.