This book primarily deals with the idea that language can influence the thoughts and actions of the people who speak it. The main character lives on a pastoral world with a very weak language, and basically all the main spacefaring races can push them around. Political intrigue sends the heir to the throne into exile on to a science/tech world with a very technical language. He studies there for years under a tutor who is the same man who rescued him during the political upheaval at home.
He eventually returns home to reclaime his throne, aided by his tutor. However, his tutor, being a science type, has an experiment in mind. He has created new languages and wants to use them on select regions of the planet. One is a very aggresive language to create a warrior caste. The next is a language which views everything in terms of value and transaction used to create a merchant/manufacturer caste. The third is a technical language similar to the one used on the science world mentioned earlier used to create a science class.
The main character thought this was a good idea because it would allow the people of Pao (the name of the planet) to become competitive in all those realms so they won't be getting pushed around anymore. The main character had, in fact, been getting worried about that even before his exile. It should be mentioned that his tutor had one main demand in return for putting this system into place: thousands of Paonese women for him to have children with. It eventually turns out that his tutor has more up his sleeve with the "experiment" than it first appeared, and numerous machinations and plans prepared for the now powerful Pao.
This report prepared by Isaac Brown