It's not completely random. I've just tried sticking sections of works by authors mentioned in this thread in to see if it can identify them, and it's not doing badly.

I gave it a slice of Finnegan's Wake, and it told me it sounded like James Joyce. It would be a pretty bad algorithm if it couldn't identify James Joyce.

Then I got it to correctly identify passages from Dan Brown and Mario Puzo. Quite impressive.

One possibility is that it's just matching word frequencies. To check this, I tried a few strings of my own devising:

"mafia mafia don don mafia mafia" --> Mario Puzo

"vatican conspiracy vatican conspiracy vatican conspiracy" --> Dan Brown

"oh woe is me, life sucks, everything is crap" --> Chuck Palahniuk