If you're not much of a series reader... I wouldn't even start.
And no, you will get no sense of closure from reading just the first book.
Don't get me wrong... I love Martin's writing and some of his characters are the most memorable I've read, but I absolutely hate his choice of format (plus I think he's starting to "wing it").
But if you're going to read it, read it before watching the series, I say.