The Valley of Fear -  Arthur Conan Doyle
So far this is my least favourite of the Sherlock Holmes novels. Holmes appears and solves the mystery, of course, but most of the book consists of back story in which neither Holmes nor Watson appear. There is nothing at all wrong with the prose, but the narrative, while interesting enough, is hardly compelling. Overall, I much prefer A Study in Scarlet and The Hound of the Baskervilles. There is simply not enough Holmes in this one for my taste.