'Rule of Two' is a sequel to the book 'Path of Destruction' and follows the Star Wars story immediately after the demise of the Brotherhood of the Sith, some 1000 years before Episode I of the Star Wars movies.
Darth Bane has taken on a new apprentice Zannah and works to instill his beliefs in her about the true way of the Sith. Though also immensely powerful in the dark side, Darth Bane is quite different to Darth Sidious/Palpatine from the Star Wars movies. He doesn't seem to crave power for himself, rather he seeks to build a legacy and immerses himself in Sith lore. Bane trains his new apprentice Zannah in the ways of the Sith, informing her that one day she will be ready to challenge him for the place of Sith master, and then take an apprentice of her own. The importance is in maintaining the Sith order and acquiring knowledge, so that one day a Sith may vanquish the Jedi and rule the galaxy. A hugely patient philosophy, almost Jedi-like. These aspects of the story give it a real edge. However, despite their attempts at secrecy, Bane and Zannah are eventually discovered by a group of Jedi leading to a climactic battle between agents of the light and dark sides of the force.
The book makes for good reading but as you know what is going to happen in the future there isn't the same level of surprise as events unfold (a little bit like reading the Silmarillion after watching Lord of The Rings). It doesnt have the same amount of action or character development as 'Path of Destruction' but I still rate it very highly.