Heh.
To experiment, I copied in progressively more of The Shadow Over Innsmouth. I started by pasting in the first paragraph, and then added one at a time.
Here are the results:
# of paragraphs - style
1 - Jack London
2-5 - David Foster Wallace
6-12 - Dan Brown
13+ H. P. Lovecraft
In other words, it takes at least 13 paragraphs of one of Lovecraft's most iconical stories to be correctly identified as being in his style.
In a second test, instead of inputting the paragraphs cumulatively, I inserted them one at a time. Here is who the analyzer thinks wrote the first 13 paragraphs of Shadows Over Innsmouth:
1 - Jack London
2 - David Foster Wallace
3 - David Foster Wallace
4 - Ursula K. Le Guin
5 - Arthur Conan Doyle
6 - Dan Brown
7 - Stephen King
8 - James Joyce
9 - Dan Brown
10 - Kurt Vonnegut
11 - Charles Dickens
12 - James Joyce
13 - H. P. Lovecraft
Out of curiosity, I took the tenth paragraph, which is identified as Vonnegut, and tested to see the minimal changes I could make to change the style. Changing "Railroad" to "road" makes the style come up as Le Guin. Interstingly, however, changing "war of 1812" to "war of 2812" makes the style be identifiable as Lovecraft.
Finally, I typed in the first paragraph of lovecraft backwards (from a word-order point of view, not letter by letter), and it still identified it as Jack London - it very clearly is just looking for keywords, and maybe properties like sentence lengths, but ignoring actual sentence structure, which is sort of crucial in these things.