BOOK ONEA Study in Scarlet is an 1887.The story marks the first appearance of Sherlock Holmes and Dr. Watson, who would become the most famous detective duo in popular fiction. The book’s title derives from a speech given by Holmes, a consulting detective, to his friend and chronicler Watson on the nature of his work, in which he describes the story’s murder investigation as his “study in scarlet”: “There’s the scarlet thread of murder running through the colourless skein of life, and our duty is to unravel it, and isolate it, and expose every inch of it.BOOK TWO:The Sign of the Four The story is set in 1888. The Sign of the Four has a complex plot involving service in India, the Indian Rebellion of 1857, a stolen treasure, and a secret pact among four convicts (“the Four” of the title) and two corrupt prison guards. It presents the detective’s drug habit and humanizes him in a way that had not been done in the preceding novel, A Study in Scarlet (1887). It also introduces Doctor Watson’s future wife, Mary Morstan.BOOK THREE:The Adventures of Sherlock Holmes is a collection of twelve short stories by Arthur Conan Doyle, first published on 14 October 1892. It contains the earliest short stories featuring the consulting detective Sherlock Holmes, which had been published in twelve monthly issues of The Strand Magazine from July 1891 to June 1892. The stories are collected in the same sequence, which is not supported by any fictional chronology. The only characters common to all twelve are Holmes and Dr. Watson and all are related in first-person narrative from Watson’s point of view.BOOK FOUR: The Memoirs of Sherlock Holmes is a collection of short stories. The twelve stories were originally published in The Strand Magazine from December 1892 to December 1893 as The Adventures number 13 to 24. For instance, “The Final Problem” was published under the subheading “XXIV.—The Adventure of the Final Problem.”BOOK FIVEThe Valley of Fear is the fourth and final Sherlock Holmes novel by Sir Arthur Conan Doyle. It is loosely based on the Molly Maguires and Pinkerton agent James McParland.BOOK SIXHis Last Bow: Some Reminiscences of Sherlock Holmes is a 1917 collection of previously published. Holmes is long retired from his profession of detective but is still alive and well, albeit suffering from a touch of rheumatism.