I got this softcover from an online seller. Looks like cheesy horror...
Later: OK, in some ways this does fit the pattern of the growing-threat-of-creepy-things-devouring-humanity, with an interesting variety of symptoms, from victims neatly hollowed out such that they seem to be just standing there, to victims being gruesomely dissolved, to - well, I'll leave the climactic monster-attacks for the reader.
There's also a running subplot in which main character Clive Thomas, a doctor with a CDC-equivalent organization, tries to convince the powers that be of his theories about the origins of the plague, while juggling marital conflicts when his wife reveals too much to a high-pressure reporter. The reporter, Robin, is also a main character, with her annoying (though understandable) professional instincts causing trouble and yet also helping to spread the truth.
The what's-causing-these-deaths bits and the monster-attacking scenes are all pretty good, and modern-day special effects could turn this into a pretty decent monster movie. But I did have issues with the subplot about the connection between Clive and Robin. It's got some familiar elements too, from their acrimonious first meetings to their coping-with-disaster-and-grief-by-falling-into-bed scenes, and while I didn't really like either of them very much - despite their attempts to save the world from the monster! - I thought their scenes together were believably messy and uncomfortable. (Robin does get at least one rather funny scene: as the city's under siege, she's tapped by a nurse to tend a room full of young children, as the nurse is needed to help with the casualties. Robin, tough and able ace reporter, stands there looking around at all the tots and infants - and "wanted to scream". She had my sympathy!
But the conclusion to all this got very dark, with [major end-of-story spoilers: Robin subjected to a brutal sexual assault - yes, in the middle of "everyone being devoured by the tendrils" - and while she reacted to this with admirable gutsiness, she lapsed into a fugue state once the crisis was over. Meanwhile, Clive's survived his mission to destroy the monster, and is cheerfully planning on the hot sex he and Robin will have... And that's how the story ends.
I... I don't know; on one hand it is a very effective nod to the trauma of sexual assault, as well as something of a Slap of Fate to the as-yet-oblivious Clive, but on the other it feels manipulative, and also pulls focus from the whole monster-story. So... your mileage may vary?]. So... a cheesy-monster-story with some surprisingly bleak psychological bits?