It's written as a normal book. But you make ink according to the first spell in the book, and it indexes and updates the rest of it. To ensure safety though you have to be a blood relation of mine to access it, or I have to write your name in the book.

[Alucard opens the first page. For him, it's a title page. For Trevor? It's blank.]

Flip through. It should be blank for almost every page, save a few dummy pages that are scribbles.