A Study in Scarlet by Sir Arthur Conan Doyle

A Study in Scarlet is a detective mystery novel written by Sir Arthur Conan Doyle, introducing his new character of Sherlock Holmes, who later became one of the most famous literary detective characters. Sir Arthur Conan Doyle wrote the story A Study in Scarlet in 1886, and it was published the next year.
The story A Study in Scarlet begins in 1881, where Dr. John Watson runs into an old friend, Stamford. Due to a shoulder injury sustained in the Anglo-Afghan War, Watson was forced to retire and is now looking for a place to live. Stamford reveals that an acquaintance of his, Sherlock Holmes, is looking for someone to split the rent at a flat at 221B, Baker Street.
Stamford takes Watson to the local hospital's lab, where Sherlock Holmes experiments with a reagent for haemoglobin detection. Watson reveals that he is willing to split the rooms at 221B and he and Holmes list all of their faults to make sure that they accept living with each other. After seeing the rooms, the two move in.
Watson is amazed by Sherlock Holmes, who has profound knowledge of chemistry and sensational literature, very precise but narrow knowledge of geology and botany; yet knows little about literature, astronomy, philosophy, and politics. Sherlock Holmes also has multiple guests visiting him at different intervals during the day; he reveals to Watson that he is a consulting detective, and that his guests are clients... (Summary by Wikipedia)