I really hope for a book 5. For me personally, Book 3 was my favorite. I do love how it loops back to the beginning. As an ending, I think it's decent. Though like you said, before the trailer I was thinking book 4 would be Amelia and Hazel and really wanted to know what happened with that. Other shows have been brought from the death of cancellation multiple times. Both Futurama and Family were cancelled 2 times So there's hope.