Project Gutenberg has millions of public domain books which are free for everyone.
These are books whose copyright period has completed. You can always find a great book in the list.
Check out the books here
Naval is giving his great book for free on his website for a long time.
You can get the book by the link below
Record main lessons and stories used to explain those lessons in an easy to retrieve format.
You can make a docx file like this.
I have used it for long. Makes an archive of great book lessons. It can be used to revise great nonfiction books.