The Reason for God is the book I used to start learning about Christianity from an Agnostic's standpoint. I was giving Jewelz a really hard time about her faith every time she would bring it up, arguing every point I could think of from a secular standpoint, so I thought I should do my due diligence and read this to at least try to understand where Christians are coming from. It is a thoughtful, well-reasoned book (although I did not agree with all of his points).
Your decision to believe in God (or not) and all of Christianity boils down to ONE thing: Jesus. You either believe that he's a fraud and none of it is true, which then means you are free to believer whatever you want... OR you believe that he is who he said he was, and therefore the implications of that require you to learn about what he taught. There is no in between. You cannot sort of believe in Jesus. You either believe that he is the Son of God, or you don't. If you want to pick and choose what to believe, then you can write your own Bible.
Here are notes on the two most important chapters (in my opinion) from the book about Jesus's life:
Chapter 12 - The (True) Story of the Cross
Chapter 13 - The Reality of the Resurrection
Hopefully, they can help you make a decision about Jesus for yourself.
The video study companion brings together a group of non-Christians with Timothy Keller to talk about some of the biggest questions that are preventing them from exploring Christianity further. I took a few notes on interesting points (definitely note representative of the entire series), but I highly recommend watching the segments for yourself.
1 - Isn't the Bible a Myth? Hasn't Science Disproved Christianity? (no notes)
2 - How Can You Say That There Is Only One Way to God? What About Other Religions? (no notes)
5 - Why Is the Church Responsible for So Much Injustice? Why Are Christians Such Hypocrites? (no notes)