Tom Shippey, in his book J.R.R. Tolkien: Author of the Century, explains how several polls in the U.K. in the 1990s demonstrated superior popularity of Tolkien's The Lord of the Rings.
… late in 1996 Waterstone’s, the British bookshop chain, and BBC Channel Four’s programme Book Choice decided between them to commission a readers’ poll to determine ‘the five books you consider the greatest of the century.’ Some 26,000 readers replied, of whom rather more than 5,000 cast their first place vote for J.R.R. Tolkien’s The Lord of the Rings…. The result was greeted with horror among professional critics and journalists, and the Daily Telegraph decided accordingly to repeat the exercise among its readers, a rather different group. Their poll produced the same result. The Folio Society then confirmed that during 1996 it had canvassed its entire membership to find out which ten books the members would most like to see in Folio Society editions, and had got 10,000 votes for The Lord of the Rings, which came first once again. 50,000 readers are said to have taken part in a July 1997 poll for the television programme Bookworm, but the result was yet again the same. In 1999 the Daily Telegraph reported that a Mori poll commissioned by the chocolate firm Nestle had actually managed to get a different result, in which The Lord of the Rings (at last) only came second! But the top spot went to the Bible, a special case, and also ineligible for the twentieth-century competition which had begun the sequence.
I know it's my favorite novel.