Retro Books: Lord Kalvan of Otherwhen by H Beam Piper

        Lord Kalvan of Otherwhen is a 1965 science fiction novel by American writer H. Beam Piper; it is part of his Paratime series of stories, and was expanded by other writers (mainly John F. Carr) to form the Kalvan series. It recounts the adventures of a Pennsylvania state trooper who is accidentally transported to a more backward parallel universe. It is Piper's last science fiction novel.
        The book is an expanded version of the novelette "Gunpowder God", which had been published in 1964 in Analog Magazine. "Gunpowder God" itself is a Paratime-series rewrite of the unpublished story "When in the Course", which takes place in the Terro-Human Future History milieu.