This book single-handedly taught me how to cook Indian food and I've cooked almost every recipe in it. It's been in print forever, and one of the simplest, best and most authentic books on Indian food I've found. It's recipes are mostly in the Northern Indian tradition, although there are some Goan vindaloos. I cannot recommend this more!
This book was suggested to me by an Indian woman as a great source for recipes. While I agree, I find that many of the recipes are a bit more involved than I have time for. But the taste is always great.