Christianity: The First Three Thousand Years

Despite the intimidating page count, this is a fantastic introduction to the whole history of Christianity. It begins well before Jesus, placing the formation of Christianity into its broader world context, and continues right up to Benedict XVI.

For such a huge undertaking the book is thoroughly researched (and referenced!), easy to read, and wryly humorous. It is entirely non-judgemental on what we might now today call mistakes made by the Church (by the same token there was no crowing about successes, either), but MacCulloch doesn't shy away from tackling those hard topics with the same even-handedness he shows the whole topic.

For an academic student of the Church, without a religious affiliation, it has been an invaluable addition to my collection and my brain.