Rick Bayless's Mexican Kitchen is an early book which has been reissued. It is a gem.
Good discussion of different chiles and several very useful and easy to make salsa recipes.
I find Diana Kennedy fascinating and almost anthropological in her approach-but a little overwhelming if I just want to cook something.
In addition to a variety of fresh and dried chiles, some other common flavors/foods are:
Corn in various forms
Garlic (moderate amounts)
Chipotle in adobo
Chorizo (different than Spanish Chorizo)
Crema (sour cream)
Cotija (aged), Chihuaha (melting) and Fresco (crumbly white) cheeses
Mexican oregano (much different than European oregano)
An easy cheat if you have a Mexican market near you is Ancho Chile powder. It's more like flakes than an actual powder, at least the stuff I buy is. It also seems to have a bit of salt in it. It gives a nice jolt of chile flavor without the effort of roasting and grinding or soaking whole, dried chiles. There are also a wide variety of prepared Mole paste bases available. Even Rick Bayless uses some of these on his show occasionally.