Even though I feel like the book's topic is redundant, looking at the things around me, I also firmly believe that many people must read it. The primary idea is basic: do not overcomplicate the design and think about the end user. If there is a "human error" in using a product, there is a system design error. Unfortunately, we're too eager to blame users for misusing something (looking at you, antennagate), whereas the designers are the ones who have failed.
For instance, consider simple glass doors. Have you ever been in a situation where you pulled when you needed to push? This is precisely the issue with bad design. Good design leads the user to the correct actions with cognitive psychology and constraints. There is no room for error when one cannot fail at a task. Remember how you had so many different screws and bolts assembling a piece of IKEA furniture? This was done partially so you don't screw the wrong bolts into the wrong places.
A broken sofa isn't the only way failure to use a product can be unfortunate. Sometimes, bad design leads to detrimental results. E.g., the Hawaii false missile alert happened due to a button's alleged lousy design. Instead of pressing the "test" button, the operator pushed the "live" button. Pushing into production, amirite? Or even worse things can happen when medical devices administer life-saving (or threatening, depending on the dose) drugs. What if there is no constraint and someone uses an imperial system instead of a metric? Actually, we know what happens — NASA loses $327,000,000.
Anyway, back to the book. Don advocates for a simple design that sets the user up for success, not failure. He underlines the importance of avoiding featuritis — that's when you add too many features to a product. In my opinion, if you have two features on launch — you have already failed; you most likely need only one feature. Remember Gall's Law?
This is also the philosophy I use when developing software and launching products — hence, for me, the book was "meh." I've learned all the lessons in my own exploration. However, again, I'd love as many people as possible to read "The Design Of Everyday Things", so go pick up a copy!