The little green book?
It's about a girl and her family + several other families, who are leaving earth to find a new planet because the planet isn't really livable anymore. They get in the space ship and finally find a planet and land and it takes em a while to figure out how they are going to live. The biggest deal is that everyone going can only take one book (because of space on the ship) and the MC picks a green book full of empty pages so she can keep a journal. Really an amazing story. Or that's how i remember it.
ANyway, does anyone know what book I'm talking about. I think it was like 100(ish) pages and I really want to find it again, but every time I search the title I seem to find more stuff about the environment then about this book.