James Anderson recently published this book:
It's a twofer: both an introduction to Christianity as well as a defense of Christianity. Although Dr. Anderson is very sophisticated, he writes with a light touch. Very accessible for the nonspecialist.
We live in an age of militant secularization, so this book is good, both for intellectually beleaguered Christian laymen as well as open-minded unbelievers who don't know the first thing about Christianity, and just assume it's intellectually indefensible.