There's nothing quite like this book. Damn, that's an understatement. If you're interested in the intersection of physics and spirituality, or if you've ever wondered what the universe has to do with you, be good to yourself and check this book out. It's a slog, to be sure, but it's well worth it.
The main premise is this: from two simple assumptions (the existence of consciousness and of evolution) Mr. Campbell produces a complete theory and working model of the entire universe. Among other things it explores themes of consciousness, evolution, the physical/non-physical mechanics of reality, and our role as individuated thought-packets in contributing to the overall lowering of entropy of the universe. Mr. Campbell is a highly-credentialed physicist by trade and it shows, but at its core, this is in fact a spiritual text.
It's written in language that's academic and verbose and sometimes too dense, with a humorous, kindly tone. (I think the average syllable count per word might be, I don't know, 4?)
I'm guessing this book has gotten so little coverage or attention because it's 800+ pages, like I said before, of very dense language and very heady ideas. (The author even places milestones throughout to congratulate the reader for "making it this far.") Another reason might be that sometimes the things which are hardest to argue against are also, for some reason, the easiest to ignore.
Anyway, this book'll clean your room for ya. By that I mean it'll give you some very solid conceptual groundwork to start living a life of exploration, purpose, and love. I'm writing this in 2020, nearly 8 years after picking this book up for the first time. I'm revisiting the book again and remembering all these wonderful ideas that opened my mind like a flower back in college. I may have forgotten the details, but in my own way I've lived with the ideas in this book, I've done my best to put them to the test, and they have validated themselves, and enriched my life, many times over. So thank you, Tom Campbell, for giving me my world view.