These books are not the same as how we RP on this site. On our site we usually have the Player who created the RP to give us a background of what is going on, in story form, in their characters eyes. Once they do that they would give the current situtation like any normal story.
If they have any special request that they would like to happen in the RP they would put that in brackets at the end of their post. SImple as that. The next player who is willing to join will post a beginning to their character, perferably meeting the other character and together, will form a story.