Jennifer Egan did a New Yorker story called "Black Box"[1] that was intentionally composed as sub-140 character chunks. It was released on Twitter tweet-by-tweet and collected in a New Yorker science fiction special last year.

She is an impressive and experimental writer (check out her "Visit from the Goon Squad") who does a great job with this form. The thought-sized chunks give the story a lot of space and cleverly invites the reader to imagine a lot of context.

[1]: http://en.wikipedia.org/wiki/Black_Box_(Jennifer_Egan_story)