@Fa5t3r - I think it was the travel memoir that really got the ball rolling on popular nonfiction titles. Between Bill Bryson, Elizabeth Gilbert and Frances Mays they got the attention of the majority of book readers (and movie goers).
Although, to be honest, I'm not sure that travel memoirs should even be considered to be nonfiction books, as they always seem to be constructions of real events and fiction encounters (that might have happened, but in reality didn't occur).
Which is not to say that I don't like travel memoirs. I actually prefer them to reading guidebooks, because they almost always have more detail, even if it isn't always the most useful details.