Hey there. I have two ideas that seem fun to me
The book you have been writing either:
1) sucks the writer inside the world of their own creation and must survive and return home. If they die in the story not only will it cease to exist but they author will die with the story.
2) The book characters, protagonists, antagonists and others come into the real world. Their powers are a bit less than before but the main goal is one they share: to find the person who created them.
One person is the real world writer and the other is the fictional characters. We can talk about plot once I attract some interest.