I have noticed that this book receives some bad responses, but then that is not surprising when you have a book that is purporting to outline all of the evidence supporting the authenticity of Christianity. Unfortunately it has been a while since I read it but it is one of those books that ordered as notes as opposed to being written in prose to make it easier see the evidence that McDowell agrues. However, the problem, as one person suggested, is that there are a lot of logical fallacies and a lot of assumptions.
One of the fallacies that I want to point out (which I do believe comes from this book) are the number of copies of the New Testament that we have, and the dating of these documents. In reality the earliest copy of the New Testament we have is the Codex Sinaticus (you can see it on display in the British Library) which dates back to about 500 AD. While we do have a lot of documents that predate the codex, they all tend to either be fragments, or single books, so when they talk about the oldest New Testament document that we have we are actually talking about a fragment. The same goes with the number of gospel documents we have, because once again a bulk of them are fragments. How is it that we claim that the oldest copy of the Republic we have dates to around 800 AD, when in reality we have fragments that are much earlier (and the same goes with the Iliad and the Odyssey). We Christians love to criticise and attack atheists for using logical fallacies and twisting the truth, when in reality we do it ourselves all the time.
Look, there is a lot of evidence for Christianity, and the fact that it is one of the dominant religions of our time, which has doctrine that is almost unchanged from when the apostles first wrote their creed, is evidence enough, and I also have no argument against using or studying apologetics to defend our faith, however, as the Bible says, the key word here is to defend and promote our faith, not to destroy, ridicule or undermine other people's faith. In many ways I do not necessarily say people are wrong, but rather they have an understanding that is leading them in the right direction.