253
Interactive fiction came up briefly at the panel about online fiction markets at Readercon today. The one title mentioned was 253 by Geoff Ryman. With the help of someone else’s tweet about it, I looked it up once I got home. While certainly non-linear, it turned out to be less interactive than I expected. (This is not a Choose Your Own Adventure story.)
On the other hand, there’s an interesting drabble aspect to the story, with each page being exactly 253 words long.
See this GeekDad post for the latest Choose Your Own Adventure news, the Wikipedia article on gamebooks for more general information, and gamebooks.org for links.