The plague of monsters started with an interesting silver beetle, found during a nature study project on the grounds of an isolated boarding school in the north of England. It ended in a blood-bath. The silver beetle was not alone--there were other creatures, half metal, half alive, who spread their strange infection with every bit and claw wound, turning victims into hideous creatures of destruction.
And soon the peaceful school becomes a scene of horror, as classmates and teachers fall to the silver scourge, and the survivors watch as their friends mutate, and turn against them.
Which results in our hero, Paul, and a (rapidly dwindling) number of other kids (including a bully, a geek, and It girl, and a wanna-be It girl, ineffectually led by the science teacher) holed up in the science building trying to fend off the silver creatures. And it is very exciting, as the creatures are evolving in both intelligence and in specialized abilities. The boards nailed across the windows soon (and horribly) become inadequate...
But Paul finds reserves of leadership he didn't know he had, and the other kids step up to the plate...and it becomes a fast read indeed as one wonders how on earth anyone is going to make it out alive. (One also wonders, as do the protagonists, if there is anywhere safe outside the school to escape to...)
Creepy tunnels beneath the school, teeming with really nightmarish monsters, a very creepy school swimming pool scene, and lots of death in general make this a good one for readers with a tolerance for horror. And though the protagonists seem at first to be rather stereotypical, sufficient layers of characterization are added to allow the reader some emotional investment in the outcome.
Here's what I found scary--the scientific premise behind the creatures. It's all too easy to imagine ways in which we can mix hubris and technology to create monsters...
Here's the Kirkus review, and here's Ms. Yingling's revew
disclaimer: review copy recieved from the publisher