This novel is poorly written, poorly edited, and poorly conceived. It has a respectable - and obvious - agenda, but does that agenda a great disservice.
First, the book is full of grammatical errors and misused words. For example, Shafer consistently uses the word "parameter" incorrectly in place of "perimeter" and he has real problems with subjective, objective, and reflexive pronouns (his editor should be ashamed).
Second, Shafer's Bible scholarship is questionable: characters refer to Eve by name long before she and Adam are cast out of Eden (in the Bible, she isn't named until after God discovers that they've eaten the forbidden fruit); characters refer to animals in Eden by name before Adam is created (Adam is the one who actually names the animals); Adam & Eve are forbidden to eat the fruit of the tree of knowledge of good and evil AND the fruit of the tree of life (in the Bible, God only forbids them to eat of the former, but evicts them from Eden so they won't eat the fruit of the latter). I understand that Shafer is writing about events that might have happened, but he could have worked much harder to reconcile his additions to the story with what is told in the Bible.
Third, Shafer includes debates and logical discussions throughout the book, but the logic he uses is replete with fallacies and holes. After Lucifer asks several non-rhetorical questions, another character remarks that Lucifer speaks the truth (questions can be neither true nor false, only valid or invalid - it's the answers to those questions that are true or false). The debate that takes place near the end of the book is little more than a barrage of ad hominem fallacies, name-calling, and red herrings. All of this is pointless, though, since faith is not dependent on logic.
All in all, this book was very disappointing, and I would encourage anyone seeking good Christian literature to look elsewhere.