I love H.P. Lovecraft and I love Sherlock Holmes. This novel is a mix of these, so I thought "Why the hell not?".
This isn't a bad novel by any means, it's well written by someone who nows the original material very well. And yet, it somehow falls short. This simply felt like a Lovecraftian tale where the main characters happend to be Holmes and Watson. The whole is not greater than sum of the parts.

Another thing I didn't praticularly like. There's a (probably necessary) trick the author uses (a little too often) to have Lovecraft's and Conan Doyle's canons fit together: Watson at some point states something like "You know when in 'A study in red' I said that thing? Well, that's wasn't true. This is what really happened.". Well, it feels a little too much like cheating to me.