David Ash is a woman-magnet, a scruffy middle-aged, alcoholic, ghost-hunter, sullen and emotionally closed off - except when he isn't (he does have a tendency to fall in love quickly and deeply throughout the trilogy). One reads the book suspecting that Ash may be a fantasy projection of James Herbert himself.
This book, while longer, isn't as good as the previous two. Most of the characters are tropes and there is no further development of the central character. Instead it's full of conspiracy, violent haunting, and revenge.
Knowing what I know now, I probably would have finished the series with book two. For anyone who wants unrelenting action and doesn't care about character arcs, the book will provide all you need.
I read some other reader reviews after posting mine on Goodreads, and some people think this is the best book EVER! Thus the Marmite comment in the title.