Though I don't like thinking about societal decline, I observe it happening. So, I think it's only prudent to inform myself about what's coming my way.
The first chapter consists of facts that Clarey takes as indicators of our decline. It was review for me, but clearly, he was using it to burst bubbles for anyone who hadn't informed themselves about the state of affairs. It's out of date, since the book was written in 2013, but most of the indicators are still trending in the same direction.
Some chapters after that carry general advice about focusing on the essentials of living, and not dedicating yourself to a career, but working for yourself as much as possible. He talks about how to get what you want out of life with a minimal amount of money, to avoid the tax burden.
He makes a depressing case for "caving," and getting on government programs whenever you can, because you're paying for them (even if you're not paying taxes, you're still paying for them, due to the devaluation our monetary policy creates, along with the public debt), and our society is never going to turn away from them. So, you might as well use them. The last part of the book is dedicated to the "SHTF" scenario, which is conceivable, but perhaps not in my lifetime (I'm 50). Younger folk may want to pay more attention to that part. It's a survivalist guide.
Despite the depressing talk, he stresses that you should live the best life you can, and talks about how to do that (seeing sights you want to see, enjoying the finer things, finding friends, and spending quality time with those you love, etc.). That is the best revenge against those who are bringing on the decline (he goes into what they are like, as well).