I've got a screen that is much wider than it is tall, this throws away so much of it. It's as bad as Facebook, where the stuff you want to see is a band about 1/4 the area of the screen.
On mobile, so many times it ends up creating a bad UX, but I will say that it does make more sense there where you can't change your browser width.
The NASM website is an example of this. Personally, I don't like it and would prefer a single column.
Proper column layout involves limiting columns to screen height, probably by paginating. Then the reader can perceive the text as a tree of Page > Column > Paragraph > Row. Tangentially, I think there are studies positing that this, helped by the notion of physical pages in space, is what's behind the readability advantage of books.
Alternative to pagination is scroll-direction: horizontal. Now the experience is even closer to reading a book. And to Windows 8! IMO there's a shortage of novelty sites with true (non-slideshow or carousel) horizontal scrolling.
[0]: https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Columns...