Book Eater (MKR)

Theodore Miller knows everything about magic...except how to use it. Just as he's about to fail at Berghen Academy, Theo stumbles upon a grimoire named "Gluttony" that takes the form of a magic-hungry creature on his hand. The more magical texts and artefacts Gluttony devours, the more powerful Theo becomes, swiftly propelling him to stardom as the academy's top student. Although he now faces the constant risk of being consumed by an insatiable parasite, Theo is finally on the path to becoming a genuine wizard.

Original Webtoon:
KakaoPage, Daum

Official Translations:
English, Japanese