Hi, I am from a non-English speaking country and I scored 104. (R30 L28 S19 W27). I took me about 2 weeks or so to prepare. (I had some problems with speaking part.). Obviously, there should not be a problem for a native speaker like you who got 49 on verbal.
Anyways, if you want to get the best score possible, you should prepare some, especially on speaking part. The questions are kind of a pattern. Just make yourself familiar with it and your speaking should be very smooth.
I also think that the official book is enough. Just try the practice tests in CD to see where you are at.