The majority of Kaplický's works are historical fictions spanning the period from the Hussite Wars in the 15th century to the revolutionary upheaval of 1848. His novel "Kladivo na čarodějnice" (1963), about witch trials in northern Moravia during the 1670s is the best known because it served as the basis for movie by Otakar Vávra ("Malleus Maleficarum", also translated as "Witches' Hammer" or "Witchhammer").