When the Core Rule Book is finished, it will be availble to download for free as a PDF, or to buy as a physical copy. Although it is currently 70 pages long, it is not complete, and many sections are not ready to be published.
Below is a PDF containing several sections that we are ready to show (subject to editing), which should give a good idea of how the game works. It covers turn taking/tracking, issuing decrees and espionage.