The Seven-Percent Solution by Nicholas Meyer

Under hypnosis, she claims to be Nancy von Leinsdorf, the American wife of the recently-deceased Baron Karl von Leinsdorf. Freud introduces Holmes to a catatonic young woman who has been hospitalized after a suicide attempt. What finally revives Holmes is a new mystery. Using a treatment consisting largely of hypnosis, Freud helps Holmes shake off his addiction and his delusions about Moriarty, but neither he nor Watson can revive Holmes’ dejected spirit. Knowing that Sherlock would never willingly see a doctor about his addiction and mental problems, Watson, Mycroft, and Moriarty trick Holmes into traveling to Vienna, where Watson introduces him to the psychiatrist Sigmund Freud. The heart of the novel consists of an account of Holmes’ recovery from his addiction. Moriarty also refers to a 'great tragedy' in Holmes' childhood, but refuses to explain further when pressed by Watson. Watson meets Moriarty, who denies that he is a criminal and reluctantly threatens to pursue legal action unless the accusations cease. Moriarty was in fact the childhood mathematics tutor of Sherlock and his brother Mycroft. The novel presents this view as nothing more than the fevered imagining of Holmes' cocaine-sodden mind. The novel begins in 1891, when Holmes first informs Watson of his belief that Professor Moriarty is a 'Napoleon of Crime'. The Seven-Per-Cent Solution's Watson explains that they were published to conceal the truth concerning Holmes’ 'Great Hiatus'. These are 'The Final Problem', in which Holmes apparently died along with Professor James Moriarty, and 'The Empty House', wherein Holmes reappeared after a three-year absence and revealed that he had not been killed after all.

An introduction states that two canonical Holmes adventures were fabrications.

The Seven-Percent Solution by Nicholas Meyer