Isekai manga where op is a weak magician in a hero party and gets stronger with a book

Question

I’m searching for an isekai manga where the mc is a magician in a hero party and he is weak and because of his weakness his party abandoned him then someone give him a weird book of mage that contains all kind of secrets. He gets op then with this book.

Answer 1

I believe this is "Kouryakuhon" o Kushi Suru Saikyou no Mahoutsukai ~< Meirei sa sero > to wa Iwa Senai Oreryuu Mao Tobatsu Saizen Ruuto ~, or The Strongest Sorcerer Who Makes Full Use of the "Strategy Guide".

The main character is a magician who was kicked out of the hero's party after a battle where his magic was not harming an enemy. He then buys a book from a merchant. As mentioned in the title, that book was a 'Strategy Guide' for the world he lives in. He looks up the monster the group had been fighting, and found out that the monster they were fighting was weak to different spells than what the hero insisted the magician use. The magician then became powerful with the knowledge of the best ways to fight monsters, gain xp, and find rare items.