Hi Kaila! :)
I agree with the other commentary on this thread. This is a big step for you. Congratulations. I've also recently come into my atheism. I also live in "Bi-bull Belt" America, and understand the true frustration of living in such a place. Thankfully, I've had the good fortune of going back to college and I am pursuing a Biology degree. Sadly, this does not stop the crazy from piling up on my doorstep, or knocking at strange hours to have non-sequitor discussions, intended to hold me back from my dream career. Because I recognize this, it keeps me strong and more determined than ever to achieve it. I've read a lot of great books so far to learn about this new aspect of myself, applied Occam's Razor to my formerly held beliefs that I no longer ascribe to, and strengthen my ties with other atheists and skeptics online. My science and math textbooks,(expensive, but awesome) helped quite a bit too. Remember, Cosine of Theta doesn't equal 3 and if there's anything I can offer as far as support or friendship to help you, I'm here. ;) A good friend of mine quoted: "School: The-Anti-Stupid!" I modified it to "Education: the Anti-Stupid!" because we don't have to be in college necessarily to educate our minds, although it helps a lot.
I think you are already there. You don't need to define your reasoning to people that don't don't reason.
Just say no, I don't believe.
Actually, somewhat better than any books would be this.
Wow. What a wide open question and a good one too. Let me a start with a general viewpoint and then give a few a specific books for specific areas at the end.
In general, science - the most successful method of acquiring knowledge that we have found to date - has as one of it's key properties, atheism. Now, most scientists wouldn't word it that way, they would use the term "methodological naturalism." What that term means, is that when looking for and explanation to a phenomenon, it is assumed that events follow causal (or at least statistical) chains acting under natural laws. That is to say, "no gods allowed." But this was not some ad-hoc philosophy inserted by atheist scientists to convert the pious. In fact, it became a working assumption when most professionals doing science had (or at least professed) some kind of religious belief. The reason MN became a part of the method of science was because it worked. In other words, if we want to interrogate nature to figure out how it works, the best method available to us, tells us to begin with the premise that there is no intelligent design behind this system. As I said, this was not some dogmatic decree. In fact, if the intelligent design premise had been better at explaining what we see and predicting what will see in the future, we wouldn't be having this discussion. So, has science found god? No, in fact science works better when it doesn't even look. For a general discussion of science, I agree with Joseph's recommendation of "The Demon-Haunted World." Also any good text book on the history of science. (Aliotos, "A History of Western Science" or Asimov's Chronology of Science and Discovery are both excellent).
For specifics: Evolution - Believe it or not, "On the Origin of Species." Darwin was a heck of a good writer besides being a brilliant biologist. He also answered most of the religious objections to evolution in it (shame I still have to repeat him 150 yrs later). For more recent works, Coyne's "Why Evolution is True" and Dawkin's "The Ancestor's Tale"
Big Bang - Hawking's "A Brief History of Time," Stenger's "The Comprehensible Cosmos," Krause's "A Universe From Nothing."
Does science have anything to say about the existence of god - Both by Victor Stenger; "Has Science Found God?" and "God: The Failed Hypothesis"
I know that's quite a reading list I shot at you, but hopefully you can cut it down based on the specific area you were looking for. On the other hand, they are all great reads so you may just want to read them all anyway.
Hope this helps.
Welcome to reality. I commend you for coming out with your Atheism. I recommend immersing yourself in reality content. I have compiled a list of free films, videos, website, books, etc.. to help those seeking for logic, reason and truth. My site is easy as heck to navigate because it's one page. Take a look at http://www.charliescrusade.org. Remember You Are Not Alone.
read "Why I am not a Christian" by Bertrand Russell.
Kaila - Skeptics Society is a great ongoing source for critical and rational thinking in all regards, most particularly religion and science. They also have a weekly email newsletter.
I like this very short video of Bertrand Russell.