What was the name of the book written by Cotton Mather about the trials?

The book Cotton Mather wrote about the Salem witch trials was Wonders of the Invisible World.

More fully titled The Wonders of the Invisible World, the book was published in 1693, while the trials and their aftermath were still being debated. Mather presented accounts of alleged witchcraft as historical and theological evidence, arguing that the Devil was attacking New England’s Puritan communities through human agents.

The work defended the prosecution of accused witches and helped justify the proceedings, although Mather did not serve as a formal judge. It included accounts of several cases, including that of Martha Carrier, and reflected the period’s belief that supernatural forces could operate within ordinary communities.

The book soon became controversial. Mather’s father, Increase Mather, published Cases of Conscience Concerning Evil Spirits around the same time, but that was a separate work. In 1700, Robert Calef answered Mather with More Wonders of the Invisible World, a forceful criticism of the trials and of Mather’s role in defending them. Historians continue to debate how much influence Mather had on the prosecutions.