A cooperative book writing system where several people can write a book together.  There are many people with different skills who would like to write a book but never get the time or motivation to finish writing the entire book.

The system, a password protected website would allow people to work on the book by constructing it from the basic elements.  Writers with a keen sense for big picture would plot the major plot points and character arcs.  Once the ending is vaguely finished, you put easter eggs and foreshadowing through the earlier chapters. 

For differences of opinion, they vote on the direction of the story.

Then the conversationalist writers, if different from above, will fill in the dialogue to get the characters through the story.  Perhaps a creative person could speak into a dictaphone if a transcriptionist type would enjoy putting it into writing.

Then someone to make sure the story makes sense, there is no plagiarism, and editors to check the spelling and grammar.