if you can get your hands on a copy of "voodoo in haiti" by alfred matreaux, (should be able to on amazon.com for a couple of bucks), its a decent starting point. its pretty dry writing-wise, but gives a pretty good idea of the practices, deities, history, etc.
new orleans voodoo is even a bit off from haitian voodoo and there is a book called "voodoo in new orleans" that i see all the time used, but after leafing through it i never bother to buy it. and of course, there is the book that goes with the deck. but i am sure that there are plenty of people on here who are a lot more well-versed in it than me. i never practiced, just grew up around it.