"A Study in Crimson: Sherlock Holmes 1942" by Robert J. Harris is a thoroughly enjoyable homage to Sherlock Holmes, narrated as ever by Dr John Watson. The interesting twist is that it is not inspired directly by the original stories written by Sir Arthur Conan Doyle (except, perhaps, for the title). Rather it is based on the characters of Sherlock Holmes and Dr Watson first given an outing by 20th Century Fox in their 1939 film, "The Hound of the Baskervilles". This and the films that followed it, starring Basil Rathbone as Sherlock Holmes and Nigel Bruce as Dr Watson were hugely popular. They also probably fixed Basil Rathbone in the minds of film-goers of the time and generations that followed as the definitive Sherlock Holmes.
So there's a sense in which this book is a homage to a homage: and very good it is too. It is set in London in late 1942. Someone going by the name of "Crimson Jack" is recreating the murders of Jack the Ripper on the same dates he committed them in 1888. Has the Ripper somehow returned from the grave? Is Crimson Jack a descendant of the original Jack or merely a madman obsessed with those notorious killings?
Scotland Yard turns, of course, to Sherlock Holmes for help finding the killer. Sherlock has already worked out the identity of the original Jack the Ripper, but will that help uncover the 1942 murderer before he can complete his tally of death? As Holmes and Watson tread the blacked-out streets of wartime London, death waits just around the corner.
The start of the central strand of the story is preceded by a slightly odd excursion at the government's request to Scotland to resolve what turns out to be a slightly odd mystery. We stumbled a little over this: but it doesn't matter, because the protagonists are soon back in London and drawing readers into the genuinely interesting puzzle at the heart of this book.