The show is great on its own. But in my opinion, as someone coming from the "I read the books" camp, I think it would be a good idea to read them. The show can be hard to follow at times, what with the billion different characters, and on top of that the pacing is pretty awful (half the time you cannot tell how much time has passed between scenes). If you know the book, you can actually gauge how the show is progressing in both these regards and it makes things a bit easier. Plus there are just a lot of damned good scenes in the book that couldn't appear in the show due to budget/time constraints.
The best thing about this show is the casting, and with the intimate knowledge of the characters from the book that you'll have, you will really become invested in the show.
Now it's certainly not necessary to read the books. The show on its own has been more than capable in all regards, and despite the flaws above it is actually one of the better television adaptations I have ever seen. Jump in without the novels if you want to, just be sure not to read any forums or opinions on the series until you have finished watching the first season. Spoilers really will kill a lot of things for you here.