Kadokawa’s light novel Grimoire of Zero (ゼロから始める魔法の書) has already released the long-awaited mobile RPG of the same title produced by Gree. Characters from the original novel are all included in this game.
Zero kara Hajimeru Maho no Sho is writen by Kakeru Kobashiri (虎走かける). Set in an alternative fantasy universe, a nameless half man half beast mercenary goes after The Book of Zero with a witch called Zero in order to become a true human.
The anime adaption started running in April and is still on-going.
Official website: http://d-game.dengeki.com/zeronosyo/