The Graveyard Book is written by Neil GaimanNeil Gaiman wrote Neverwhere. Neverwhere has genre FantasyNeverwhere has genre Fantasy
[Human]: Could you recommend a book similar to The Graveyard Book? [Assistant]: Are you interested in other books by Neil Gaiman, or would you prefer something in the fantasy and children's literature genre? [Human]: The Fantasy genre sounds the most preferable of the choices. 
You might be interested in The Maze Runner or The Hunger Games in that case.