The book opens when Eragon who is a remote boy from a remote valley discovers a dragon egg. When the dragon egg hatches, it is nicknamed Saphira and the two are linked for life and he assumes the only person alive with a rare and powerful status of a Dragon Rider. The king Galbatorix who is a dragon rider becomes evil himself pursues Eragon and Saphire the Dragon. The king's sinister and inhuman agents kill Eragon's uncle Garrow who helped raise him and burn his farm and this makes Eragon to flee with the village storyteller, Brom, who was also a Dragon Rider. Brom guides Eragon in what he needs to know and he later dies defending him. The two are later led to a hollow mountain called Farthen Dur that has both a dwarf city where human resistance fighters called the Varden have their temporary homes. An army in Galbatorix's services attacks Farthen Dur. Eragon manages to kill Durza with the help of Saphire and an elf named Arya although he sustains a serious wound across his back in the process.
In the aftermath of this battle, Eldest opens up. Eragon realizes that he learns to learn more and he takes advice from the elf who calls himself The Cripple Who Is Whole so that he can learn the magic of fighting. During this fight, the stability of the Varden is threatened when the leader of the group is killed in a follow-up attack in Urgal operation. During this operation, Eragon's friend Murtahg and some sorcerers called the twins disappear. The Varden choose their fallen leader's daughter, Nasuada to lead them. Eragon and Saphira wo by now are important figures are asked to endorse Nasuada's choice to which they agree. Nasuada moves the Varden to the free land of Surda to which they plan another attack against Galbatorix. As they plan to leave the land of dwarves, the king choses to adopt Eragon as an honorary member of his family.
As the story unfolds, we discover that Eragon's cousin called Roran returns to their rural home hoping to marry Katrina, the butcher's daughter. But the village is surrounded by some imperial soldiers who are led by Galbatorix's sinister agent Ra'zac who are looking for Roran. Although the villager's resist, they are overpowered by their opponents who vow to destroy the village. Ra'zac captures Katrina and these angers Roran who organizes the whole his community to travel enmass to Surda to join the resistance. The journey is tough with many hardships and this makes Roran to be atough and sometimes ruthless leader. Meanwhile, Eragon, Saphira, Arya, and a dwarf named Orik travel to Ellesméra which is the elves capital to train. Eragon later becomes a powerful magician and a mysterious dragon magic alters his form such that he takes the strength and appearance of an elf instead of a person. He falls in love with Arya who rebuffs his many advances because she is old and an elf princess.
Through magical means, Eragon and Saphire realize that Galbatorix's army was organizing an attack to join Varden in the battle. Roran arrives via a stolen boat and he makes a contribution to the battle. Eargon fights with all his might but as they continue with the battle, one of the two eggs in Galbatorix's box hatches and murtagh is now a Dragon Rider who does Galbatorix's will. As the fight ensures, Murtagh reveals to Eragon that they are brothers. Eragon's other parent is a treacherous fighter who betrayed the order to follow Galbatorix. Although he is more powerful, Murtagh lets Eragon escape. Eragon goes to meet Ra'zac and they decide to meet each other brother and they decide to kill Ra'zac and rescue Katrina.