First detective novel

According to the British Library, the first modern detective novel is The Notting Hill Mystery by Charles Felix (UK), which was serialized in the magazine Once A Week between 1862 and 1863, and published in its complete form in 1863. The novel starts with a murder and slowly reveals the twists and turns leading up to the crime, establishing many of the classic features of the now-ubiquitous detective genre. The Notting Hill Mystery predates Wilkie Collins's The Moonstone (1868) and Emile Gaboriau's L'Affaire Lerouge (1866), both of which are often cited as contenders for the first detective novel.

The British Library describe the book: "The story is told by insurance investigator Ralph Henderson, who is building a case against the sinister Baron ‘R___’, suspected of murdering his wife in order to obtain significant life insurance payments. Henderson descends into a maze of intrigue including a diabolical mesmerist, kidnapping by gypsies, slow-poisoners, a rich uncle’s will and three murders. Presented in the form of diary entries, family letters, chemical analysis reports, interviews with witnesses and a crime scene map, the novel displays innovative techniques that would not become common features of detective fiction until the 1920s."

Charles Felix was the pseudonym of the lawyer and journalist Charles Warren Adams.