First off, if you're looking for the book that the insanely awesome Life Force movie was based on, this is it. No wonder they changed the name for the movie, haha.
Anyway, the first 50 pages or so of this book was just rocking as hard as a pirate ship in a hurricane. Some space explorers come across a 50km derelict ship floating around, with insanely huge fixtures, stairs, badass gothic cathedral architecture, weird artwork involving Lovecraftian squiddy things, and some naked people in suspended animation behind glass walls that open telepathically. And they are space vampires. And in the ship there is a map of ancient Greece. Holy shit, the stage is set for some badassery.
Unfortunately, that's about all the badassery we're going to get. As another reviewer has said on this sight, it's mostly talking heads, scientists, cops, politicians, all talking about vampirism, parasitism, then a couple of nicely-placed scenes that follow, to give examples of what everyone was just talking about. I won't give away the ending, even though it's not that awesome, but just want to say that if Colin Wilson had handed in the first 50 pages to the publisher and said, "Ok, here's the rest of the story, blah blah blah," then had the publishers pull in, like, Dan Simmons or someone like that to finish it up, would have been the best sci-horror novel ever. But, he fucked it up.