"Both Rings were round and there the resemblance ceases," wrote J.R.R. Tolkien about the rings in his epic The Lord of the Rings and Richard Wagner's opera cycle The Ring of the Nibelung. Or did he? The answer is not as straightforward as many Tolkien fans believe, whether they agree with the statement or consider it misguided. Nor is the statement itself as transparently defensive as some Wagner buffs suggest. Much has been said and written about Wagner and Tolkien, a subject that tends to generate a certain amount of heat, mostly due to the former's controversial status as Hitler's...