Shame I'm on European time! The Sword of Shannara had a huge impact on me when I first read it in the early 1980s. When I stumbled across Elfstones a few years later, when I was 13, I read it in less than a day. (And I had a bit of a crush on Brin Ohmsford from Darrel Sweet's cover of Wishsong.)
I've always loved how the subsequent Shannara series show the evolution of the world. It's so easy for fantasy authors to keep telling the same stories in the same setting. It takes guts and skill to move the world forward and create new stories.