A Blook is, according to Hackoff.com, "a book serialized on a blog. You can read it with a browser or feed reader, subscribe to it, tag it, comment on it, and link to it."
Hackoff.com is a blook... The story is essentially a murder mystery set in the midst of the dot-com bubble. Check out the personal blog of the author, Tom Evslin, for more insight into it's creation. In addition, he's also kind of taken an alternate reality gaming approach, as there are fake websites, press releases and other materials that factor into the story.
There may be a high learning curve to really understand and get involved in what's happening, but it's an interesting idea, and feels like something different. Thanks to Jason for the link.