"The Case for Christmas" by Lee Strobel.

The best part of the books were

1) the interview with the historian that made the case for an early writing of the Gospels, and the book of Acts and

2) the interview with the Jewish man who set out to read the Old Testament, looking for prophesies of the Messiah, and found them fulfilled in the Jesus of the New Testament.

Other than that, a lot of the book was telling Christians what they already know.  It's a good book to know and have, because it lays "what we believe and why" out so clearly.