Well actually te need to think about it the first book Eragon was named after the most important person Which is Eragon himself. Then there is secondo book Eldest which più o likely means Oromis. Third book was called Brisingr which was a very important key in Eragon because he needs a new sword then he gets one. So if te havn't noticed all the titles are either a name,title o object.
Just thinka bout it Eragon was important in the first book so it was named after him. Then Eldest which più then likely means Oromis. And finally Brisingr for the sword he gets. Basically all the names are a Name, titolo and object. Inheritance wouldn't fit Besides the already used inheritance for the first 2 libri He calls them the inheritance cycle. Also the Eldunari are Eragons only chance just like Eragon was the only chance against Galbatorix, and like eldest it was important to see oromis, and last of all Brisingr he needed that sword to help him kill Galbatorix. So how is this different? I mean Eldunari are very VERY important to Eragon right now.
