--Contains Spoilers--
First, let me say that I like Sherlock Holmes pastiches. That makes me a pariah with some Holmesians, but I like them just the same. That said, I am the first to admit that they are decidedly a mixed bag. Some are wonderful, some are dreadful; most fall somewhere in between in the 'pretty good' category.
I picked up Sherlock Holmes & Mr Hyde by Christian Klaver because I had credit at the book store and nothing else there worked for me that day. But I do like crossovers with other Victorian fiction, so it seemed worth a try. If I'd realized at the time it was the second book in the series, I might've paused, but probably would've taken it anyway. I've begun series in the middle before, and, as I said, there was little else to choose from.
It wasn't hard to gather the threads of what had happened in book 1. However, the world Mr Klaver created there is so complex, he has to spend paragraph upon paragraph expaining it to the reader. This doesn't make for entertaining reading for the new reader, and I can't imagine how tedious it would be for those familiar with the first volume.
That was difficult to put up with, but there are other things I find harder to endure. Excepting Holmes and Watson, the good characters are portrayed as evil and the evil characters as good. Vampires, werewolves, even Hyde himself, are clearly meant by the author to be sympathetic, which doesn't work for me at all. I like my heroes flawed, but good, and my villains multi-faceted, but evil. And I think it shows a lot of cheek to take a classic like The Strange Case of Dr Jekyll and Mr Hyde, and say that Stevenson got it all wrong. Nope, doesn't work for me at all.
I suggest you read Loren Estelman's Dr Jekyll and Mr Holmes instead. In my opinion, it does more justice to both the original sources.
