I haven't been able to find much written about it on the web, not even at the Google blog. It seems to be a more visually interactive version of Google Docs, on which several people can already collaborate. The Story Builder formalizes who is writing what, and lends itself to dialogue.
|Screen shot of Story Builder|
There's a very limited selection of music you can add to your creation. When you click "Finish Up" the story will be sent to Google Docs, and you can share it to Google+, too. A link to the story is generated. Click here to view my "Odd Conversation from Homer" ( http://goo.gl/DYkqW)
(Text for the story courtesy of Project Gutenberg)
Give the site a moment to load the audio.