A top British official described Salman Rushdie's novel "The Satanic Verses" as offensive but said there could be no justification for Iran's death threats against its author. "We understand that the book itself has been found deeply offensive by people of the Muslim faith," Foreign Secretary Geoffrey Howe said, adding: "We cannot allow the overturning of the principle of the freedom of speech." Howe went on to distance the British government from the views expressed in Rushdie's book, saying: "It compares Britain with Hitler's Germany. . . . The book is offensive about our government and our society and we resent that." Howe plans to meet in Vienna on Monday with Soviet Foreign Minister Eduard A. Shevardnadze, who has indicated a willingness to mediate the dispute.