The reasons I love this book: 1. There is only one person in the world who could have written it, I think, and luckily enough he did. 2. The prose is beautiful if often only semi-relevant. 3. The (very real) depiction of the medieval church and its infighting touches on one of my favorite branches of European history. 4. I positively eat up "philosophical fiction." (5. I have since read Anathem, which is Il Nomen in modern prose, with space, and am convinced it's the best book of the 21st century. And equally certain none of these are.)
I kinda liked "Diamond Age", but as usual, he didn't do that great a job wrapping it all up at the end. Like "Snow Crash", the concepts in that book stuck with me, though - and it's also short enough to not be too mind-numbing by the time you reach the end.
To be fair, it's pretty easy to tear Tolkien a new asshole. He was a linguistic genius, and he created a world, history and creation story in full technicolour, but he wasn't very good at talking about it. I think if someone else had taken his source material and written LOTR it would actually be a much better book.