Phantoms is a promising concept ruined by lackluster execution.
Jenny Paige returns to her hometown of Snowfield, Colorado to find it deserted. Going house to house, they discover a few bodies dead or badly mutilated. Eventually an older police officer whose mannerisms sounds suspiciously like Columbo, is alerted and arrives in the town with a few of his men one of whom is very rude and perverted and guess who gets turned into a monster first and has his head eaten off by a giant fly you're right.
Phantoms creates a creepy atmosphere up front (much like another book I recently reviewed), but can barely sustain it past the first 100 pages. When the creature begins revealing itself in the form of grotesque bugs and the bodies of those who've been killed, it's a little eerie. When it happens for the 600th time, it's grating.
In regards to the creatures orgins, the book flirts with a lot of the same ideas as Stephen King's Desperation, but doesn't have the guts to follow through with them. It's suggested that the creature is Satan himself, and that the book is somehow a metaphor for the world... but actually, the monster is some creature who was born from the primodial soup but never really left it behind. Evil Gak, you might say.
Anyway, this book wasn't very good, but it was better than The Homing, so I give it a 3/10. As far as promising concepts? I'm a sucker for creepy towns.