From publisher blurb:
The sanity and madness rules presented enhance role-playing, create challenges for the players, and bring more color to your game. 5th edition characters are, above all else, exceptional. They are capable of winning virtually any fight, overcoming epic challenges, and creating miracles. These rules keep that spirit in mind.
The 20 pages of new rules build upon the framework provided by the DMG. There are expansive tables for transient, short-term, long-term, and indefinite madness, with nearly 50 different entries describing the narrative and mechanical effects on the character.
For DMs looking for more color without the added mechanical crunch the narrative descriptions provide ample fodder for you and your players to role-play.
Lamp's Light Custom form-fillable character sheets