This is a very useful book for Christians who have grown up in or are currently living in an environment where belief in evolution is discouraged, but want to investigate the evidence for themselves. There seems to be very strong opposition to evolution in evangelical circles in the US, though that's far less true here in the UK.
For me, the issue mainly hinges on how to reconcile evolution with certain Biblical theology. For instance: if we believe the evidence points to humans having evolved over millions of years, how do we approach the question of sin and the atonement? At what point during the evolutionary process did God begin to hold humans accountable for sin? If sexual behaviour is evolved, why does God condemn homosexuality? How do we account for spirit and soul? These questions and many more are absolutely fundamental, in my opinion, following the acceptance of the evidence for evolution.
Sadly, this book covers none of the above questions. He does a wonderful job of presenting the scientific evidence for "gradual creation" (he's very careful to avoid the term "evolution"), but makes few attempts to reconcile the theological and philosophical questions it raises. He does make some references to scripture, but I felt they were a little half-hearted, and I was even quite unconvinced by his interpretation of some passages. I'm happy to accept that Falk's strong suit is science, and regrettably I'll need to look elsewhere for a theological angle.
I think this book could make a good reference in discussing evolution with other Christians who have been exposed to anti-evolutionary arguments in the past.