The Book of Truth is a powerful artifact: It contains the absolute truth abouth everything, and any change on the book will alter reality itself, and now it's on the hands of Liana, a competent if not precisely powerful mage who pretends to use it's powers for herself.

However, even with all this power Liana remains a coward who is too afraid of the power of the book to just turn herself invincible or all powerful. Fearful of others who would want to take the book from her she intends to transform those potential threats under her control, and you just so happens to be one of them.

Sucks to be you. Unless you can take the book of her, of course.