I am a 21 year old fairly recent "convert" to Atheism - I use quotes because conversion signifies religious undertones. There is nothing religious about Atheism, rather it is simply the acceptance of logic and the elevation of one's mind above fairy tales.
I officially became an Atheist six months ago, after many years of internal debate and strife. The credit for my conversion actually goes to Ayn Rand and her book Atlas Shrugged. The lack of proof for God wasn't what converted me necessarily, but rather the lack of objective morality in religion. I never believed in the religious belief of sacrificing your happiness, dreams, life, etc. for others. What about my happiness? Doesn't that matter? It's funny - Christians claim that Atheism leads to people feeling worthless but I can tell you that as a Catholic, you truly feel worthless. If you, sir, have never experienced Catholic guilt, I would suggest that you stay away far away from it. It is the most damaging and destructive force on the mind and the soul.
Still, you have had a great impact upon my progress as a young and budding Atheist. "Coming out" to an Irish-Italian Catholic family was certainly not easy but I am fortunate in that my parents have accepted it. Your book gave me the courage to accept that what I believed was not something to be ashamed of. Indeed, it's something I should be very proud of.
It's very weird, being on the other side of arguments. For years, I used to argue in favor of Creationism, miracles, banning stem cell research, etc. (please don't hate me for it) but now I am completely on the opposite side. I reject mysticism of any kind and hate religion's intrusion in government. It's funny when I get into religious debates now because I know exactly how my opponent thinks. It's a very powerful tool to win arguments with.
Just recently I got into a debate with a Catholic about Christianity and he used a line that would have made you laugh. I, using your argument, said that Christianity like any other subject should be open to debate. We can debate political theory, so why not religious theory? We got onto the Old Testament and he said, almost word for word from your book, "But you know Christians don't believe in the Old Testament anymore! You know the New Testament replaced all of that!" I wished you could have seen it, sir.
To paraphrase Penn and Teller - if this book doesn't change the mind of whoever reads it, we will have some serious issues. Thank you for your book, sir, and keep up the good fight.