Phantoms is forty five minutes of made-for-TV-level haunted house horror, and then forty-five minutes of scientificky sci-fi hoo-ha with soldiers and the dog from The Thing, but an adorable golden lab instead of an inscrutable husky..
I'm normally very careful about spoilers, but I feel that Phantoms is fair game for two reasons: 1) it's over ten years old, and 2) it's really really bad.
I read that book and thought it was AWESOME. ...but that was in 1983. I was 14. Even then, I thought the second half, post-reveal, got pretty lame. I never bothered with the movie, as it appeared to be as Tom described.