The choice Justin made to have goliath culture not use books is indicative of this season as a whole...

...considering the defining feature of the wizard class is the Spellbook*

*/uj RAW you're allowed any kind of transcription-capable object to serve as a spellbook. So you can justify using the characters tattoos or beaded cords to record your spells.

However, Justin specifically cites their *oral* tradition of information retention, meaning he made culture that doesnt transcribe for their all-wizards campaign