I've never actually read any of Joyce's works. (One attempt to wade through Ulysses put me off.)
The above result was pretty consistent -- I fed it different chapters from all three AQ novels, and even chapter one of AQ4, and got James Joyce every time.
I am skeptical about the analytical algorithm used (which is not described). I suspect that it's based on simple n-grams, rather than any actual parsing of sentence structures. When I input chapters from Hogwarts Houses Divided, I was told I write like J.K. Rowling, and when I input something more recent and non-fanfic related, I got Douglas Adams.