At a cultural fair this weekend, I picked up a free copy of the Quran at an Islam booth. I've been meaning to get that and the Christian Bible and finally read them both at some point, but I haven't gotten around to it. There are a few other ancient classics that have had a huge impact on history and human culture that I want to read, too - Tao Te Ching, The Analects of Confucius, Sun Tzu's Art of War, etc.
Next time I stay at a hotel, I'm stealing the Bible. I used to think that wasn't allowed, but I recently learned that the people who put them there are happy when they disappear. Maybe I'll see how many different holy books I can pick up for free. I hear the Mormons are always giving out free copies of the Book of Mormon, too.
But I haven't actually started reading any of these yet. Currently still working through The God Delusion by Dawkins. While I agree with pretty much all of what I've read there so far, and I'm learning some interesting information, I'm not a huge fan of his writing style. I can see where all the complaints about him being too abrasive come from.