Eternity clearly means forever. It is a physical place, a destination, as well as a state of being. Heaven is the forever life destination. Hell is the forever death destination.
Questions arise when you consider these forever destinations. For instance, why does a person go to heaven? How does he get there? You can ask the same questions about hell. Defining eternal life will help answer these questions.
Jesus defined eternal life when He said: "This is eternal life, that they may know You, the only true God, and Jesus Christ whom You have sent." (John 17:3) What Jesus is referring to is a personal relationship between man and God that lasts forever. God created man for relationship.
Taking relationship into account, the answer to the above questions becomes: You go to heaven because you have a relationship with God and you go to hell because you don't.
Choice is required for relationships to exist. You must choose whether to enter into a relationship. In this book I examine how choices in relationships leads to the eternal destinations of either heaven or hell. God has placed humans into a world of choice from which it is impossible to escape. You cannot choose to not choose because even that is a choice!
Overall, this book is about what it means to be a Christian.