This is arguably the book that almost single handedly initiated the 1960's Occult revival and all the various schools of thought for good & ill that came from it. It certainly contributed to the resurgence of interest in Gurdjieff from a insulated teacher of movement & the Work to global mega-star of the consciousness movement. It also served to inspire a variety of "ancient astronaut" theorists including von Daniken and his ilk.
After the seminal works of Charles Fort, this was the second generation bible of speculative thought on a grand scale. Long out of print, it is welcomed to see it back and available to a new generation of readers. Some of it will seem dated no doubt and at times a bit histrionic, yet this is the work that set many psychonauts on the path for the "other" wherever that may lead.
I first read this book back in the late 70's, and it was a classic back then. As far as I know, it's been out of print for a very long time, but led an active "retirement" via book swaps and used book sales.
The authors touch upon hundreds of different subjects and events, weaving an occult history of the world, liberally seasoned with speculations, asides and suggestions.
Anyone who has ever had the feeling that there's more to the world than what's readily apparent needs to read this book. This book will be especially valuable to those who want to educate themselves in occult matters, as it provides several very good starting points to further research.