Here are a couple of real world examples. It's a common phrase that I've heard as long as I can remember. It's an opinion of somebody that it's something highly worth reading. No one can force you to read it though.
TCM (Turner Classic Movies) even has a movie segment called "The Essentials" which is their list of must-see movies. (Essential watching )
Over the last decade, RIIA® has identified books, papers, articles and blog posts that have moved the discussion about retirement and retirement planning solutions forward and incorporated them into our essential reading list.