"Kouryakubon" wo Kushi Suru Saikyou no Mahoutsukai: <Meirei Sasero> to wa Iwasenai Oreryuu Maou Toubatsu Saizen Route

Magnus, a wizard who gets ordered around by the hero, is kicked out of the party. Right after that, he receives a book written in the language of the gods detailing all the information he would need to defeat the demon king-the ultimate strategy guide! (Source: Manga UP!)