An Icelandic company has plunged the country’s powerful publishing industry into a debate about censorship with its plan to publish a 1976 book that persuasively argues the Holocaust is a hoax: The book, an Icelandic-language translation of “The Hoax of the Twentieth Century: The Case Against the Presumed Extermination of European Jewry” by Arthur Butz, is being advertised online ahead of its...