Maybe I'm just not cut out for Dan Simmons' particular brand of mysticism. I didn't like the supernatural bent of The Terror and didn't like the supernatural bent of this book. What appears to be a suspenseful Dickensian supernatural mystery is actually, beneath the surface, an incredibly long and dull tour of Victorian London and opium dreams.
The jacket copy of this edition misconstrues the book's nature, at least in my opinion. When I borrowed this book, I thought I was getting a supernatural mystery told from the point of view of Charles Dickens (or perhaps following him from a limited third-person perspective). Instead, the actual narrator of the book is Dickens' friend and protégé, Wilkie Collins. In fact, I would go as far as saying that the book isn't about Dickens at all. It's more about Wilkie Collins, and Dickens is only involved because the majority of the public will have never heard of Collins but would love, like me, to read a book about Dickens. Now this is all well and good--I didn't mind reading a book about Wilkie Collins. I just wish I had known that going into the book.
Similarly, I shouldn't be upset about supernatural elements in a book that is supposed to be supernatural, right? Except that the entire "Drood" mystery is conflated by the prospect of it all being an opium- or mesmerism-induced fantasy. Perhaps I just dislike it when the supernatural elements aren't blatantly real but merely just suggested.
Almost everyone mentions the unnecessary length of Drood, and it's a valid point. There's no reason for this novel to be nearly 800 pages. Simmons does a wonderful job describing Victorian London, and I liked being immersed in that world. But he could have ... summarized certain episodes. The first two hundred or so pages are enjoyable, and then the book's supernatural aspect goes into overdrive, and it becomes tiresome.
This is just a book worth skipping, period. It doesn't matter how much you love Victorian London, Charles Dickens, or Wilkie Collins. There's no reason to subject yourself to Drood. The payoff isn't worth it. Go read an Anne Perry mystery instead.