A Game of Thrones – Book or Series?

Many people have been recommending that I read, “A Game of Thrones” by George R.R. Martin. I’ve read very few books in this genre – in fact that only one I can think of is The Hobbit. Having said that, for those of you who have read the book and watched the series (so far), is it still worth delving into the books now that the series is out?

Pardon the noob question, but how does this series stack up against The Lord of the Rings? (which I’ve not yet read either although it’s sitting on my shelf)