Koestler's fifth work of fiction is probably the most moving since "Darkness at Noon." It is in some ways more ambitious than that memorable novel. In "Darkness at Noon," Koestler dealt with the Bolshevik mind and the human spirit; he helped dispel the mystery of how both could be contained in a single vessel, a man. "The Age of Longing" deals not only with the Bolshevik mind, once again fellow-traveling with the human spirit, but with a number of other peculiarly conditioned minds--among them the democratic, the French, the religious, the literary the apostate and the American. In these dealings he meets with widely varying degrees of success. Finally, the book is built on the philosophic idea that the early 20th century was an age characterized by a longing for the absolute and certitude.