iirc your supposed to use the bimbonomicon with the vampire hunting mage after her glasses are broken so she neutralizes the vampire (the same day that the vampire says "no one", but you need to serve at least 4 for the sorceress to not end you, so it changes to "get rid of the vamp"), guess the alt path where you gameover yourself by giving her the normal book instead is either bugged or the dev forgot to write it that gameover.