Can you elaborate a little more? What's your row and stitch gauge according to your swatch? What is the row and stitch gauge on the pattern? (I don't have the book). If your swatch gives you the same gauge as the pattern suggests, you can use the new yarn with no problem. If not, you'll need to change needle sizes.
According to the (fuzzy) pictures on the link you gave, the top looks like it's supposed to be pretty fitted, so I would knit which ever size is closest to your bust size.