Reddit mentions of The Sword of Shannara Trilogy

The Hero and the Crown by Robin McKinley

The Earthsea series by Ursula LeGuin

The Dragonlance Chronicles by Margaret Weiss and Tracy Hickman

The Belgariad and The Mallorean by David Eddings

The War of the Blades series by J.D. Hallowell

The Shannara series by Terry Brooks

I'm currently reading Septimus Heap, Book Five: Syren

I might read The Sword of Shannara Trilogy next

Start with Sword. I recommend you read them in the order they were written. That being said, the books are wildly different than the show (in a very good way). You may not like the show when you're finished reading.

As for cheapest way to read them (as there are A LOT of them), I recommend either getting them from your library, or, if you prefer to own, going with the combined books such as this

The others mentioned some good ones, but I'll add:

I loved the Chronicles of Prydain as a kid
http://www.amazon.com/Chronicles-Prydain-Boxed-Set/dp/1250000939/ref=sr_1_1?s=books&ie=UTF8&qid=1380775925&sr=1-1&keywords=chronicles+of+prydain+box+set

Sword of Shanarra is pretty classic. The series does get long if that is what you are looking for
http://www.amazon.com/Sword-Shannara-Trilogy-ebook/dp/B000FBFMZM/ref=sr_1_2?s=books&ie=UTF8&qid=1380775981&sr=1-2&keywords=shannara+series

The Unremembered is a good new series:
http://www.amazon.com/The-Unremembered-Book-Vault-Heaven/dp/0765325713