I was also slightly unhappy with some of the events towards the end of the book. James Herbert is a renowned horror writer for a reason, but towards the end the book seemed to veer a little away from horror towards a more Hollywood action film style ending. Given that there was a fair amount of imagination required to meld semi-factual pieces with fiction throughout most of the book, parts of the ending were a bit of a disappointment. The pace certainly held up, but I wasn't entirely convinced by the direction it took.
It was the pace and the basic idea that kept me reading more so than the execution. This is Herbet's longest book and it feels like he's run into the same problem as [[:Category:Stephen King |Stephen King]] and [[:Category:Dean Koontz|Dean Koontz ]] before him in that longer isn't always better. That said, apart from David Ash's back story, this isn't a bad introduction to James Herbert's work, as it has enough to keep a reader interested and it's not going to be too unsettling to someone unused to the horror genre. But for the experienced horror reader that I am, these were the same things that took the edge off it slightly.
If you like a little more horror in your horror novel, [[Mr Shivers by Robert Jackson Bennett]] isn't a bad place to go to.