Overall I was not impressed. I have yet to read any Ken Follett (he is on my list for the next few weeks), but I suspect that his work will be similar to this novel. I know that Follett is a slave to the idea that the plot must change every 3-5 pages to keep the average reader engaged (or the idiot entertained, depending on how much faith you have in the average).
I enjoyed the beginning of this book: there was a hint of supernatural, but otherwise straightforward historical fiction. Set in Barcelona early 1900s with lots of period references and drama. BUT in an effort to keep "jerking the reader's chain", Zafon comes up with some barely believable plot twists. Most amazingly, Martin assumes when Cristina disappears after only his second night with her that she has changed her mind. This is the man who has seen non-explainable stuff for 10 years now and believes he works for the devil, but is not at all suspicious that someone might have kidnapped Cristina! Several other times Martin simply goes home and goes to bed rather than seek out answers to the mysteries surrounding his house and Corelli (I refuse to call him the boss..OMG is this a novel about the mob???).
The first 200 pages were engaging, the last 300 were slightly amusing, but not really any better than watching the heroine in a horror movie walk alone into the house where the bad guy is without a flashlight.