ELDEST

The Eldest Advanced Readers Copy is an uncorrected proof that was released to editors and reviewers ahead of the Knopf Hard Cover release in August 2006. Due to this being an unofficial release, the book has no ISBN.  These ARCs are designed to drive up hype for books before release by giving reviewers early access to books. Eragon also got an ARC, however, Christopher didn't like the idea of his work being released uncorrected. By the time Brisingr came around he had enough say to stop any more ARCs from being made. 

“I hated putting out work that wasn't fully edited, so I didn't let them do ARCs for the other books.” - Christopher