My Absorption System

Huge portals opened up on Earth, bringing along strange and powerful monsters who humankind couldn't defeat. Everything seemed lost, but one day, a human found an ability book inside a place they called dungeons.
Humanity slowly started to get back on track, and the most powerful ability books were kept hidden, only to be passed down generation after generation.
Arthur, a poor boy who didn't receive an ability book from his family, and was doomed to be bullied and buried, unable to rise his rank on society.
One day, everything changed. The ability he had always been searching for was already inside of him, asleep, and revealed itself when he turned 14...