I can think of nobody more deserving, and no honour longer overdue. In the words of the man (knight) himself:
"Marry, nuncle, if'n I had a Knighthood (Night Hood), why, it would keep my ears Warm in Bedde; i'faith, if many a Knight is a Fool, why, should a-"Congratulations, Sir Terry, and long may you continue bringing light into our lives. And now I have to find a way to send him an empty envelope with "Sir Terry Pratchett, Knight" written on the front.
In joke. If you don't get it, you need to read a better class of books.