I'd put this one at 3.5, really, but I'll bump it up to 4 because I thought the writing was excellent. I've been reading some of the old Victorian Gothics recently and the author mentions in the Q&A at the end of it that he's a fan of those. It really comes through in his storytelling, right down to a character highjacking the narrative partway through for a lengthy background story. There are some wonderful descriptive passages, too. 
 The story itself is solid, but I think it lacked a certain spark. Maybe it's because there were so many points-of-view (so, much less suspense built by limiting it), or maybe it was because of the form the Prince of Mist took in some incidences. ((view spoiler)[I think the malevolent clown thing has been overdone, even in horror for older audiences. (hide spoiler)]) 
 Still, a very enjoyable read. I'll definitely check out some of Zafon's other works.