From the publisher's website:
Playing a character is like putting on a mask: Slip on a mask, and you become someone else.
This book presents 1,000 "masks" -- non-player characters that are fun to play, and that your players will never forget. Featuring a foreword by gaming industry legend Wolfgang Baur, Masks is the ultimate NPC resource.
Think of your favorite character from a game, book, or movie. What makes them memorable? It’s not their Strength score, or how many hit points they have -- it’s who they are as a person: what they look like, how they act, their personality, and what drives them.
Using a simple but powerful template that features Appearance, Roleplaying, Personality, Motivation, Background, and Traits, Masks provides the core elements of a thousand great characters. Masks NPCs are designed to be used on the fly, no prep required -- but with enough depth to be used when planning adventures, as well.