A Study in Scarlet is a detective

Detective

A detective is an investigator, either a member of a police agency or a private person. The latter may be known as private investigators or "private eyes"...

 mystery

Mystery fiction

Mystery fiction is a loosely-defined term.1.It is often used as a synonym for detective fiction or crime fiction— in other words a novel or short story in which a detective investigates and solves a crime mystery. Sometimes mystery books are nonfiction...

 novel

Novel

A novel is a book of long narrative in literary prose. The genre has historical roots both in the fields of the medieval and early modern romance and in the tradition of the novella. The latter supplied the present generic term in the late 18th century....

 written by Sir Arthur Conan Doyle

Arthur Conan Doyle

Sir Arthur Ignatius Conan Doyle DL was a Scottish physician and writer, most noted for his stories about the detective Sherlock Holmes, generally considered a milestone in the field of crime fiction, and for the adventures of Professor Challenger...

, introducing his new character of Sherlock Holmes

Sherlock Holmes

Sherlock Holmes is a fictional detective created by Scottish author and physician Sir Arthur Conan Doyle. The fantastic London-based "consulting detective", Holmes is famous for his astute logical reasoning, his ability to take almost any disguise, and his use of forensic science skills to solve...

, who later became one of the most famous literary detective characters. He wrote the story in 1886, and it was published the next year. The book's title derives from a speech given by Holmes to his sidekick Doctor 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

Skein

Skein may refer to:* A flock of geese or ducks in V formation flight* A wound ball of yarn with a center pull strand, see hank* TV Series, used part of Variety's slanguage.* Skein dubh, a Scottish knife* Skein module, a mathematical concept...

 of life, and our duty is to unravel it, and isolate it, and expose every inch of it."

Conan Doyle wrote the novel at the age of 27 in less than three weeks.