Communion is Strieber's autobiographical accounts of his abductions and interactions with aliens. The book describes what he is convinced are real events spread over many years. 
This was a disappointing addition to Strieber's body of work. He's an excellent horror author. I tried to imagine this as just another horror story by him with a false framing story for verisimilitude, despite knowing going in that he truly believes in the abductions and alien interactions described therein. I even have some old pictures of my father reading this and tried to think of it as a way of connecting back to his experiences as a reader. I couldn't do it. I couldn't take it seriously. What I'm sure was supposed to feel menacing felt silly, what was supposed to feel hopeful felt ludicrous.  The recovered memory tropes don't work as we know in the field of psychology that they're virtually always fictitious. The conspiracy theories and paranoia come across as mentally ill. 
I guess, if you consider yourself a survivor of these sorts of abductions you'll probably enjoy this. It just makes me feel sad for Strieber though.