I think the monk had no nefarious plans for the book. He was just going to lock it in a vault (probably with 50 other dragon hunting books).

That book going to the library would have been bad. Librarians seldom work to completely remove books from circulation. They might restrict them a little, but seldom to the level of outright censorship. Hautwyrm would have been able to read that book if she visited the library.

Franz would also have just stuck it in a vault, but he might have let a heterodyne know of its existence. I get the feeling his personal library is not something even the Heterodyne sees very often.