Here are some resources I have found useful. I have read all these books. I agree with some, I disagree with some, but all have shaped the way I think about Christianity.
Holy Bible- I'm sure you've heard of it. It's pretty famous.
Reasonable Faith - Dr. William Lane Craig
This is a great book that sets forth great arguments for the logical basis for God. Dr. Craig is a professor of philosophy and has a great website called http://www.reasonablefaith.com/. Check out his book, then check out his site.
Mere Christianity - C.S. Lewis
C.S. Lewis is one of the most quoted authors within Christian circles, but I don't know if many people actually understand his positions on many things, including the problem of evil, free will/predestination, evolution, and the relationship between reason and faith. All of his books are good, but this is the one that has shaped my worldview the most.
Letter to a Christian Nation - Sam Harris
Sam Harris is very angry in this book, but there are some important lessons to be taken away for Christians, particularly in meeting the kind of thinking that "anti-Christians" use.
Creation in Six Days - James Jordan
To any Christian who think they can get away with believing in an old earth because days can be reinterpreted as "long periods of time", this is the book for you. You will be challenged by a man who clearly has a powerful grasp of the Bible. I disliked this book at first, because I was used to use the eras as days argument, but it's eye opening to say the least.
The Reason for God - Timothy Keller
Great beginning apologetics book for anyone who would like to learn more. As with every and any apologetics book, take what the author has to say with a grain of salt. Wrestle with it in your mind. Follow his logical steps and question why he took them. I think he gets lots of things wrong, but he also gets lots of things right, and the questions he asks are all the right ones when you are learning to back up your faith.
