Overall, David's thoughts on becoming a millionaire by the time you retire, using a really simple method, make sense. This is definitely a useful read if you find yourself in a spot where you're trying to understand fundamentals of 401(k)'s, IRA's, or taxes. I'm personally well versed in this information, though I did enjoy reading this to continue to cement my knowledge. There is a theme throughout the book of relating concepts back to real life examples, which I feel helps to make this information more palatable for the average reader.
As mentioned, David does a great job of introducing new concepts around automating one's personal finances. He starts with an introduction to a couple that is about to retire, earlier than average, with enough money in the bank to support themselves. They didn't do anything wild to get to where they are now, they essentially just made sure to invest in their 401(K)'s and live a relatively frugal lifestyle. From there, David jumps into how the reader can follow the same path to financial freedom within retirement. These concepts, if followed, are laid out in a way that walk you through tracking your spending so that you understand where your money goes, to saving for a large purchase like a car.
The book itself is a relatively quick read, you could blaze through this in a day or so. I appreciate that David takes the time to explain concepts without going down a rabbit hole of being too specific, while still taking the time to relate them back to real life. The concepts also work for anyone at any point in life - obviously it makes sense to start saving for your future as young as you can, (a concept pointed out in the book), but if you're picking this up later in life you would still benefit from the information inside.
The downside of having a book that's easy to digest and a quick read is that the entire book is based around one main concept. While it's good to focus on a base knowledge, this book might be a little too simple for a well read adult who has experience with their 401(k) and other basic investing principals.
The writing also focuses too much on being able to retire at the end of your career for my personal tastes. While it is definitely considered an achievement to make it to 65 and be able to actually stop working, to live off of your savings, this is far too late in life for my personal goals. If you're someone who is looking to build a base of knowledge, then use that knowledge to start making more money with investments, this book is only the first step.
Despite the information in David's book being considered rudimentary to some, I understand that not everyone reading is at the same point in life. There are varying levels of financial literacy, and this book is clearly aimed at the average American who may not necessarily understand how to get the most out of their paychecks. If you're someone who is still at the beginning phases of understanding money, then this is certainly a book to pick up.