This is the fourth and last novel in the Eragon series. It begins with a battle, as the Varden, rebels against the evil king Galbatorix, fight to capture a city. Eragon, along with his dragon Saphira, fights where there is the most resistance. The Varden need to capture every major city in Alagaesia, so that they wouldn't come after them when they would attack Uru'baen, the capital of Alagaesia, and also king Galbatorix's habitat.
When the Varden have nearly captured the city, Eragon sees a wall collapse onto Roran, his cousin. Eragon and Saphira rush to help him, but it is too late: the heavy wall has already done it's work. But, on the positive side, the wall has given Eragon a way in the castle of the Lord of the city. After he kills all the guards, he hands over the king to a pack of werecats, who helped the Varden capture the city.
Then he tries to find Roran. Eventually, with the help of Saphira and several werecats, he manages to lift away the heavy stones and free Roran.
Then the Varden continue their arduous journey towards Uru'baen. Along the way, the people of Surda and their king Orrin join them as backups.
I'll let you discover the rest. All I can say is that the book will get way more interesting later...
If you want to visit the site, here is the link: www.alagaesia.com