Lots and lots of books out there. The most important thing, of course, is what goes inside you because it will go inside your child. So avoid artificial additives, too much sugar, too much of everything you already know is bad for you, try to eat organically grown foods, you know, again, everything you already know about what goes inside of you. That includes pharmaceutical products, some of which are not safe if you're breastfeeding. If you eat well, your child eats well. As for calories, they're not that important for you or your child as some claim; the more important thing is how well and how quickly you metabolize your food and other such things, but since you're breastfeeding, none of this affects your child -- reading about breastfeeding will tell you how much your child needs and how often. And congratulations.