Readers were shocked by its sexually explicit content, and themes of rape and incest, leading it to become arguably the most controversial Gothic novel of the 18th century.

The story revolves around a devoted monk, Ambrosio, who is tempted to break his sacred vows when a young man, Rosario, reveals that he is a woman, also known as "Matilda," and comes to the monastery and disguises himself as a nun to become closer to him.

Afterward, he is as disgusted with Antonia as he was with Matilda, who arrives to warn him that the convent is burning down due to a riot (caused by the events of Raymond and Agnes's story).

Lewis summarized the story as the tale of "a holy man led by the devil into seduction and murder and tricked at the point of death into forfeiting his soul.

"[21][22] In one letter, Lewis claimed to have written The Monk in ten weeks, but other correspondence suggests that he had at least started it, or something similar, a couple of years earlier.

[25] The book continued to rise in popularity, but in a February 1797 review by a writer for the European Magazine, the novel was criticised for "plagiarism, immorality, and wild extravagance.

This, indeed, was no difficult task, for the objection rested entirely on expressions too strong, and words carelessly chosen; not on the sentiments, characters, or general tendency of the work".

[27] Lewis wrote an apology for The Monk in the preface of another work, as recorded by Peck:"Without entering into the discussion whether the principles inculcated in "The Monk" are right or wrong, or whether the means by which the story is conducted is likely to do more mischief than the tendency is likely to produce good, I solemnly declare, that when I published the work I had no idea that its publication could be prejudicial; if I was wrong, the error proceeded from my judgment, not from my intention.

Without entering into the merits of the advice which it proposes to convey, or attempting to defend (what I now condemn myself) the language and manner in which that advice was delivered, I solemnly declare, that in writing the passage which regards the Bible (consisting of a single page, and the only passage which I ever wrote on the subject) I had not the most distant intention to bring the sacred Writings into contempt, and that, had I suspected it of producing such an effect, I should not have written the paragraph".

"It looked," writes André Parreaux, "as if every reviewer or critic of the book, no matter how hostile he was, felt compelled to at least pay lip-service to Lewis's genius.

He was a reckless defiler of the public mind; a profligate, he cared not how many were to be undone when he drew back the curtain of his profligacy; he had infected his reason with the insolent belief that the power to corrupt made the right, and that conscience might be laughed, so long as he could evade law.

His nature instructs him to exult himself above others and lust for the Virgin Mary, while his religious inclinations, or at least his awareness of his position within the church, command him to humility and chastity.

[42] All of these circumstances are consistent with the classic model of the morality tale, and, true to form, once Ambrosio is tempted into sin he enters into a tailspin of increasing desire, which leads him to transgression and culminates in the loss of his eternal salvation and his grisly murder at the hands of the devil.

Robert Miles writes that "Ann Radcliffe and Matthew Lewis were the two most significant Gothic novelists of the 1790s, an estimate of their importance shared by their contemporaries.".

"[44] Similar to Ambrosio, the Marquis was tempted and succumbed to sin, which sets him on a wicked path leading to his public shame and suicide.

The rest of the story is the result of Matilda's influence over Ambrosio as she leads him through progressively unforgivable sins— rape, murder, and witchcraft—until he eventually signs his own soul over to the devil.

"[48] Admittedly, Vathek can be more readily identified as a morality tale, but The Necromancer warns against the pernicious effects of a legal system that is bereft of mercy.

The vow of celibacy, which many Protestant writers at the time condemned as unnatural, is presented as contributing significantly to Ambrosio's repressed sexuality, which in turn leads to the heinous acts he commits against Antonia.

Blakemore argues that in England, the sexual demonization of the aberrant Catholic "Other" was part and parcel of the ideological formation of the English, Protestant national identity.

"[51] Lewis also appears to mock Catholic superstition through use of iconoclasm[52] repeatedly over the course of the novel, such as when Lorenzo moves a statue of the virgin St. Clare to reveal the chamber in which Agnes is being kept prisoner.

Ambrosio has already given into his desire for Matilda and the story of the Bleeding Nun told in the subplot foreshadows his further downfall with Antonia and his eternal punishment in the hands of the devil.

When she gets into Raymond's carriage, "Immediately thick clouds obscured the sky: The winds howled around us, the lightning flashed, and the Thunder roared tremendously".

Matthew Lewis uses Gothic fiction to play a role in The Monk by reliving the terror, surprise, and horror of the French Revolution through the lives of his characters.

Therefore, Matthew Lewis doesn't use Ambrosio's sexuality in the novel to lead the reader to focus on his moral degradation but on the values that have been instilled in him since birth.

During the 1700s, the Kingdom of France established the Ancien Régime, a term for social and political structure also known as the "Third Estate,"[64] which was made up of the clergy, the nobility, and the commoners.

"[66] He speaks about how the Catholic church depicted females as always aiming to broadcast their beauty, especially the Virgin Mary and other saints, and how the novel sought to expose Catholicism by relying on the images of women.

The libretto by Salvadore Cammarano is based on a 5-act French play (1835), La nonne sanglante, by Auguste Anicet-Bourgeois and Julien de Mallian, a drama informed by motifs and imagery from The Monk.

La nonne sanglante (The Bloody Nun), freely based on The Monk, is a five-act opera by Charles Gounod to a libretto by Eugène Scribe and Germain Delavigne.

[72] Grant Morrison and Klaus Janson's 1990 DC Comics graphic novel Batman: Gothic relies heavily and overtly upon The Monk, combined with elements of Don Giovanni, as the inspiration for the plot.

[75] It was shot in Santes Creus, Girona and Madrid and stars Vincent Cassel, Déborah François, Geraldine Chaplin, and Sergi López.