One thing holds consistent across the numerous worlds of science fiction and fantasy: everyone speaks the same language. Whether it's Lojban, English, Common, or the High Tongue of the Autumn Empire; there's one language that everyone knows, unless plot demands otherwise.
Do not gather and heap up and store for yourselves treasures on earth, where moth and rust and worm consume and destroy, and where thieves break through and steal. Matthew 6:19 KJV
The spellbook of a long dead wizard that has gained the ability to read itself and cast spells from itself. If could be amazingly powerful as an ally, or use its magic to manipulate and rule a kingdom.