In the "Four Tendencies" Gretchen Rubin seeks to inform the reading about the 4 types of people you will encounter in your personal and professional life. Unlike many other personality profiles Rubin's are based on two categories. How people respond to out expectations (those put on us by others) and how people respond to internal expectations (those we put on ourselves).
The four tendencies are Upholder (Meets Outer and Inner), Questioner (Resists Outer/Meets Inner), Obliger (Meets Outer/Resists Inner), and Rebel (Resists Outer and Inner). Rubin goes on to explain both benefits and drawbacks of each tendency and makes it clear that there is no "best" tendency. What matters more is knowing how to work with your tendency as well as working with those of other tendencies.
This book can be eye opening for educators and professionals alike. By knowing these tendencies it can make it easier to deal with "difficult" people at work by showing you that they are not difficult but rather are motivated differently than you.
If interested you can take her tendency profile test online here.
I am a Questioner for the record.