This articolo is to point out the differences between the Book Eragon and the Film Eragon, which was a great disappointment to many fans, including me. So here we go, my information is from the InheriWiki.
Book- Eragon had brown hair and brown eyes. Film- Eragon had blonde hair and blue eyes.
Book- Eragon was fifteen at the start of the story. Film- Eragon was seventeen at the start of the story.
Book- The gedwëy ignasia mark is a cerchio and glows silver if the Dragon Rider uses a spell o reaches for magic. Film- The gedwëy ignasia is in the shape of an 'e'.