This is the second of two books which tell the story of a meek librarian who is transported into a parallel universe dominated by swords and sorcery.
The first book is called "Colin the Librarian" and as that title suggests, both books are parodies of the stories of "Conan the Barbarian".
Krap the Conqueror being, of course, the muscle bound hero who fights to save Colin and his friends from the evil Thargs.
If you find the names of these two books funny, you will probably find this book mildly amusing - probably not quite as entertaining as you may have hoped from the titles, but the books do have their moments.
It wouldn't be entirely fair to dismiss this as a one-joke comedy. Nevertheless, if you don't think the titles particularly funny, or have never heard of "Conan the Barbarian," then most of the jokes in this book will probably go straight past you.