The Strongest Wizard Making Full Use of the Strategy Guide -No Taking Orders, I'll Slay the Demon King My Own Way- #004

In this fantasy manga, a dejected wizard gets his lucky break after receiving a book that holds all the world’s secrets!

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!