@Rukja
Yeah, the book is basically the equivalent of a god sitting on your shoulder telling you what the best thing to do is.
pure speculation here, but the book likely updates and writes itself depending on what he does.
There is no way a book that small can hold all that information without some kind of magic.
UNLESS the book was writing just for him and ONLY contains the "basic" things he would need to more or less take over the hero role...
But even then it's kind of a stretch... ( and ofc this is all assuming the writer and the artists are actually half-competent... got to give them the benefit of doubt after all )
If that is true, then the book only has a page about her,
because he already meet her and he ( or the book ) considers her important.
That said, he really should take a look at the hero´s party pages because there is
no way they aren't important people...
Doing so could at worst let him learn their weaknesses so he can use it later if he needs to, or at best learn of a way to become the leader of the party
They still have the same goal after all, and more allies who you can trust ( or blackmail ) is a good thing...