What to read after The Sign of the Four?

Sherlock Holmes is a fictional detective of the late 19th and early 20th centuries, who first appeared in publication in 1887. He is the creation of Scottish born author and physician Sir Arthur Conan Doyle. A brilliant London-based detective, Holmes is famous for his intellectual prowess and is renowned for his skilful use of deductive reasoning (somewhat mistakenly - see inductive reasoning) and astute observation to solve difficult cases. He is arguably the most famous fictional detective ever created and is one of the best known and most universally recognizable literary characters in any genre.Conan Doyle wrote four novels and fifty-six short stories that featured Holmes. All but four stories were narrated by Holmes' friend and biographer, Dr John H. Watson, two having been narrated by Holmes himself, and two others are written in the third person. The first two stories, short novels, appeared in Beeton's Christmas Annual for 1887 and Lippincott's Monthly Magazine in 1890. The character grew tremendously in popularity with the beginning of the first series of short stories in The Strand Magazine in 1891; further series of short stories and two serialized novels appeared almost right up to Conan Doyle's death in 1930. The stories cover a period from around 1878 up to 1903, with a final case in 1914.About the book: First published in 1890, The Sign of Four is Sir Arthur Conan Doyle's second book starring legendary detective Sherlock Holmes. The story is complex, involving a secret between four ex-cons from India and a hidden treasure. More complex than the first Holmes novel, The Sign of Four also introduces the detective's drug habit and leaves breadcrumbs for the reader that lead toward the final resolution