Transmigrate Into a Book and Cling to the Big Shot

Yun Ziyou transmigrates into a book, and not just any book, but the one she just finished reading. Then, out of nowhere, a System tells her she must complete her mission in this world or be erased.

But can someone please tell her why her mission is to win over the ruthless villain?! Ugh, she has no choice. If she fails, she dies, so no matter how hard it is, she has to keep going!