To what extent do we as humans have free will and to what extent has God predestined our lives?
When discussing the true nature of free will, I believe that Jonathan Edwards little book on the Freedom of the Will is a great place to start. He defines his terms and develops his arguments in a clear and concise manner.
He is a little difficult, but it would make a great place to start. Go through the terms, understand what is at stake and press on from there.