Scrivere libri. Mano dal mantello.

YourBook is a very limited, turn-based collaborative writing tool.

You can start your own book, start writing and others will see the characters appear on their screens as you write them.They can also request to join! Tapping the "plus" icon at the bottom of the screen will place them in a queue. When their (or your) turn comes, a text field will appear to let them (you!) write. Users not present in the writing screen when their turn comes you miss it.

WARNING: the app is (as the name suggests) a bit... incomplete. You can sign in/register but you cannot log out. Future versions will limit the time & the character count for each turn. Creating a book is completely free now but it may require an in-app purchase in the future. I don't know, I may also change course completely, make it open source and join Doctors Without Borders.