Strieber was already an established novelist with two books, The Hunger and Wolfen, adapted into well-known movies.

Communion is his autobiographical account of alien encounters and abductions, involving himself as well as his family and friends—sometimes just as witnesses, sometimes more directly involved.

It's an interesting and compelling account although, as seems always to be the case, there isn't anything verifiable or documented to help the unbiased reader decide what to make of his story.

Mental illness and substance abuse don't seem to be relevant here. Strieber himself is admirably open-minded about his experiences, willing to consider that everything could be happening inside his head.

Since what he experienced is so vivid and has at least some elements observable to others, he makes the excellent point that even if all of it is inisde his head, it should be a very important area of study.

When he starts to hypothesize about what the creatures he encountered might be, things start to fall apart a bit. Since there isn't any concrete evidence or information at all, they might be anything. He makes an argument, for example, for creatures who share a hive mind.

Sure, that seems possible. As does literally everything else. Nothing in particular points to a hive-mind intelligence.

It's a well-written and affecting book, though, and worth reading. It was made into a movie starring Christopher Walken and Lindsay Crouse, which is also worth a look, even though Strieber himself was disappointed by it.

The first line is "This is one man's attempt to deal with a shattering assault from the unknown".