Some opinionated facts:
1) Every avid golfer should at least read through the book, even if they don't plan to adopt what Hogan considered to be his "fundamentals".
2) It's important to note that the 5 lessons wasn't written as a book at all, rather a series of 4 weekly instructional articles for Sports Illustrated, followed by a fifth lession, the overview and recap.
3) The target audience was the average golfer (guy who shoots around 100) to drop 20 shots and break 80 by correcting basic faults and focus on a few things. It wasn't aimed at the beginner, or at the guy trying to consistently break par, the advanced golfer.
4) The series does not mention roughly half or more of the strokes in the game, as it does not address putting at all, or chip shots or sand shots or specialty shots. As a result, it deals with a small fraction of the 30% of the game... Hogan thought the mental aspect represented 70% of the game, and the series doesn't deal with that at all. "In this series we will certainly not be attempting to cover all of golf or even one-hundredth of that almost inexhaustible subject."
5) Each "lesson" was meant to be practiced daily for a week, with the suggestion that the first lesson on the grip be practiced 30 minutes per day, for a week.
6) The series was a collaboration between 3 men: Hogan, Herb Wind, and Anthony Ravielli, and it reflect the contributions (good and bad) of each of them.
7) The book leaves out critical detail (intentional or unintentional) to understand the meaning of the words, and there are some mistakes (and many more things that are subject to multiple interpretations).
8) Although Ravieilli took film movies of his instructional sessions with Hogan to prepare the book, some of the illustrations were drawn from "poses" struck by Hogan that don't actually match what he did in his swing... as a result these illustrations are misleading, and don't match up to what Hogan himself actually did.
9) Hogan taught his students whom he personally coached to find their own way based on their physiology and not to emulate the look of his swing.
10) Although flawed and narrow in scope and incomplete and misleading and limited in its application to a particular audience, and the product of a collaborative effort, and geared toward equipment that was shorter, flatter and heavier than used today for hitting balls that were softer and spun a lot more [ etc., etc., etc.] The Five Lessons remains one of (if not) the best instructional series ever written.
Understaning Five lessons for what it is, and for what it is not, it will remain a fine work of instruction in the basics of the game for long after we're gone.
Those who invest the time to come to understand the meaning of the words (through their own experience) will treasure it. Hogan wanted people to practice and work hard, like he did.