The three greatest living authors.

A week or two ago I succumbed to the ‘ask me three questions’ meme. Most of the questions asked were fairly run of the mill and easily dismissed, but twicedead threw me a proper curve ball: who, in my opinion (he asked) are the three greatest living authors?
This question is a complete bugger and a half, but I said I’d think about it and come back to it, and so I am.

( How do you pick three from so many? )