The work was published in 2 volumes that dealt with the extensive investigation into occult matters regarding the apparitions of angels, demons and other spirits.

It included dissertations on various topics of magic, sorcery, witchcraft and instances of vampires, revenants and individuals returning from the grave.

He delved into the use of the scientific method, biology, psychology, chemistry, etymology and investigated the history of various legends of folklore to determine whether a claim of hauntings, apparitions or magic were truth or fraud.

The first tome contains 52 chapters and mostly deals with the apparitions of spirits, angels and demons while also covering the study of magic, sorcery and witchcraft.

After being rejected, he gave her philters to make her love him which occasioned strange developments in her health and proceeded to continuously give her some other forms of medicament.

During the exorcisms, the demon that possessed her made detailed and fluid responses in varying languages including French, Greek, Latin, Hebrew and Italian and was reportedly able to know and recite the thoughts and sins of various individuals who examined her.

There was even a mention of how the demon interrupted an exorcist, who after making a mistake in his recital of an exorcism rite in Latin, corrected his speech and mocked him.

[A 1] As Calmet amassed numerous reports on events of vampires, his attempt to refute false claims of vampirism proved difficult: [T]hey see, it is said, men who have been dead for several months, come back to earth, talk, walk, infest villages, ill use both men and beasts, suck the blood of their near relations, make them ill, and finally cause their death; so that people can only save themselves from their dangerous visits and their hauntings by exhuming them, impaling them, cutting off their heads, tearing out the heart, or burning them.

[B 3] The count also received other information of another man dead for more than thirty years that was reported by family to have come back to his house on three separate occasions during meal time.

This story was retold by Sheridan Le Fanu and adapted into the thirteenth chapter of the novella Carmilla, a work that heavily inspired Bram Stoker's classic Dracula.