Being a Crichton-esque book I was sort of expecting a certain degree of suspension-of-disbelief to be necessary regarding the science aspect of the story, but wow..... just ..... wow. A bit more research might've been nice. And as others have said, the ending was incredibly lazy.
I see this is going to be made into a movie, which seems appropriate. Volcano movies just about are required by some sort of unwritten law to be terrible.
I'm giving it one star because burying it under a pyroclastic flow isn't an option.