Like all ufo/paranormal books this offers absolutely nothing other than stories, you would think that after the multitude of encounters, landings and other phenomena someone might have got one tiny piece of physical evidence, or at leat a photo that wasnt taken from 30 miles away and blurred.
The main gist of this book, that governments around the world are covering up alien contact, I find very implausible, because humans and by entension governments, are incredibly stupid and incompetent, so keeping this kind of secret for 60 odd years is unlikely.
A large part of the book is taken up by cattle mutilations, which the author thinks is being carried out by aliens and/or an evil government cabal; this is the most ridiculous part of the whole idea. Even if we accept the premise that aliens would come all the way to earth to cut a cow up why leave the bodies on the ranches or arouse suspicion?! Dump it in a lake or use your alien laser telepathy or whatever to vaporise it!
The government doing it is even more insane, the idea being that they are testing chemical warfare products or something; which they could do on any number of animals, and actually do it in private by buying them perhaps? No, why not fly to a load of remote ranches, mutilate farmers livestock (which for some reason they cant source from anywhere else) and then leave the bodies for the farmers to find the next morning. Yeah right.
Then we have perhaps the most interesting part of the book, an account by a Bob Lazar who claims to have worked at Area 51 on alien spacecraft. Its a good story, but if we were able to use and replicate alien anti gravity technology I think a hell of a lot of people would be billionaires right now selling hoverboards and the like.
This ranks alongside the Von Daniken and Setchin, a money spinner for the gullible.