Although several reviewers found Gardner's final novel self-indulgent, pretentious, or pedantic, Mickelsson's Ghosts is Gardner's most ambitious and complicated work since The Sunlight Dialogues. Its form appears to be very loose, partly because Gardner employs elements of five distinct subgenres, and its focus is on the protagonist's preoccupation with philosophers, especially Nietzsche, and his tendency to relate his actual experience with the ideas of the philosophers he has studied.

The five subgenres of fiction working simultaneously in Mickelsson's Ghost are: the mystery story; academic novel; novel of ideas; sociological novel; and ghost story. Some commentators have mistakenly associated this book with the detective story, but Mickelsson does not take on the task of solving a crime. The solution is in effect thrust upon him. Professor Warren of the Chemistry department at the university where Mickelsson teaches was murdered before the novel begins, and Mickelsson's problem student...