Everything you need to understand or teach The Game of Empire by Poul Anderson.
The Game of Empire is an adventure story set on faraway worlds in a future in which humanity has not only traveled to the stars but has created a huge interstellar Terran Empire. Diana Crowfeather is a teen-age girl who survives on the streets of Olga's Landing, a bustling city full of beings from many different worlds. She has an adventurous spirit and seizes on the first chance she gets to explore other worlds. She ends up involved in an intricate and menacing plot to subvert the Terran Empire and hand it over to its worst enemies. The action is exciting and the characters are deftly created, making for an entertaining read.