I found some samples of Eureka and Masks on Engine's website and was very impressed with the information, samples, and ideas provided, so I decided to buy the full ebook for both.
This book is very well written and provides lots of easily NPCs with great physical descriptions, backgrounds, motivations and some sample storylines to go with them that work with any system.
I've already used a couple of the NPCs with little or no adjustment and the players in my game absolutely loved the detail and interaction these new NPCs provided.
I also love the name generator banner that is on each page. By flipping to any page and picking a first name from one page and a last name from the other, you can come up with 100s of new character names. It would be nice to have an index of first/last names in a table or something that would allow for quicker lookup or even a roll chart.