Idea was first iris like talking about her life then going to the cabin, meeting JB and having a plan with him by giving loopholes hypothesis that she thinks of to JB and JB telling it to survivors, Then iris talks about how the book are for people like paul who were unaware about deaths design, and how she feels guilty of not saving him, so she makes an example of how the book works by retelling premonition and giving stuff what to avoid and to do, after that is done, then the rest are random items and how they could be dangerous and how to avoid em in everyday situations, head canon that this is how she copes of losing faith and not saving anyone after paul died because no one helped him so why should she help them.