You decided to visit your friend Susan, because she was basically the most intelligent out of the entire school, because despite being the goth girl in your school, she read a lot of books which had some major good features with confusing info. It's mostly because Susan one day plans to become an investigator after college.
After you gave the book to Susan, she looked through it, and found a bunch of categories where the monster girls were made from different types as you scroll through the front page that was shown on the first page. You heard of monsters before, but you never would expect them to have so many forms. Susan however had an idea about the book, as she decided to show a page from the book which would show a monster girl based on which species the monster girl looks like.