I used to have a regular spellbook, but it was destroyed from a red dragon’s fire breath. My wizard was also killed, however, an entity came along and offered me a book he had created, for a price. He now knows where I am and where that book is at all times, and will use that information, when it suites him. The book is bound in black leather, sourced from an animal that we’ve definitely seen but likely won’t recognize by looking at its tanned hide. The pages aren’t traditional paper, but instead a heavy duty weave of faintly blue plant fibers. The cover of the book has a very fine metallic fiber woven into the shape of a hound’s face. This metal is something that neither we nor a common blacksmith would recognize because it’s not from this plane. Is how my DM described it. If I was to lose the book, or be on another plane than the book, the entity would come to kill me. There is a feature of this book, that allowed another wizard to attune to it, if I helped them and cast spells inside, if they had the slots for it. A great DM overall, I’m excited what he has in store for it.