Take the plunge! Read the first book first. You know the basic story from the show, but you're missing the hugely detailed world the author creates, which is the main attraction of fantasy novels. Also, the book describes a grim, dark, festering and stinky, unfair world that the glossy TV show does not portray as well. The TV characters are all fairly easy on the eyes, whereas in the book the characters aren't like that, especially Tyrion. The book will read quickly for you since you'll be able to keep the characters straight from the start. I don't think you'll find it redundant, and if you do, then skip to the second book.