Book in the background - https://www.amazon.com/Adventure-Time-Encyclopaedia-B-G-G/dp/1419705644
​
Here's an amazon link where you can buy it for the kindle app. If you're asking about where to illegally download it, that's not allowed on the subreddit.
Adventure Time!!!
and i'm thinking Grimm would be a matching/fitting system. anyone have a better idea?
also, i could get content from here! http://www.amazon.com/The-Adventure-Time-Encyclopaedia-Encyclopedia/dp/1419705644/ref=pd_sim_t_3