Challenging the prevailing belief that Mark Twain's position on religion hovered somewhere between skepticism and outright heresy, Lawrence Berkove and Joseph Csicsila marshal biographical details of Twain's life alongside close readings of his work to explore the religious faith of America's most beloved writer and humorist. They conclude not only that religion was an important factor in Twain's life but also that the popular conception of Twain as agnostic, atheist, or apostate is simply wrong.

Heretical Fictions is the first full-length study to assess the importance of Twain's heretical Calvinism as the foundation of his major works, bringing to light important thematic ties that connect the author's early work to his high period and from there to his late work. Berkove and Csicsila set forth the main elements of Twain's "countertheological" interpretation of Calvinism and analyze in detail the way it shapes five of his major books—Roughing It, The Adventures of Tom Sawyer, Adventures of Huckleberry Finn, A Connecticut Yankee in King Arthur's Court, and No. 44, The Mysterious Stranger—as well as some of his major short stories. The result is a ground-breaking and unconventional portrait of a seminal figure in American letters.