Well of course, you'd want to tell no one where it's kept or what you write inside of it. That's step 1 to a successful journal! Lol
I would take out a pen and edit the book. Also, see if it has an author. And try to find out more about the stranger, of course.
But that's actually a good inquiry. Who created the book? If we destroy the creator is fate now in our control or would there be total chaos?
However, the author should be YOU. It is your life. Don't have someone else dictate what you're outcome will be like. That's what I said earlier, the whole thing was skewed in itself, because it is predetermined.