[Darby]

This is a tough one.
The best writer?
Tolkien does go on a bit long with the travelling and the travelling and more travelling. And some of his heroic speeches kind of clunk.
But I do think the books are brilliant and if I had to save just one book out of all of mine, It'd be the LOTR Trilogy (and I could argue that it really IS one book, not three, lol!).
It's hard to compare LOTR with other books on a purely literary level, because the novels read more like a history. I love LOTR not because it's great literature, but because it seems real. The parts that don't work on a literary level, work because they make the book seem more authentic. Pardon if I offend anyone, but in my opinion it's like the Bible. The Bible would make a terrible novel. No consistent plotting, loose ends everywhere, variable voice, etc...
But... it's the Bible! How could we ever hold it to a literary standard? How could we ever imagine editing it?
That's what LOTR is like to me.
As for a beautifully constructed *novel* (and I won't hazard a guess as to whether it's "best"), I always think of Swordspoint by Ellen Kushner.