He's probably turned a bit to popular historian for most of AskHistorians, but I'm a big fan of Bart Erhman, especially if you are interested in the foundational debates of Christian Theology. I particularly like Lost Christianities.

Justo L. Gonzalez, "The Story of Christianity, Vol. 1" covers the emergence of Christianity up until the Protestant Reformation. It's a very easy read, and has a lot of good information in it. I've gone back to it quite a few times since I bought it.

Hi. There are a whole bunch of books on this Subject, but as an introduction, I would recommend:

Lynch, Joseph Howard: Early Christianity: a brief history. - New York, NY 2010

To help yourself to further reading, you should have a look at: Harvey, Susan Ashbrook (ed.): The Oxford handbook of early Christian studies, Oxford 2008

For a general overview, I teach with Gillian Clark's Christianity and Roman Society. Slightly dry but thorough and useful. Good to pair with Martin Goodman's Rome and Jerusalem.

For a larger look at the turning points in the history of Christianity, Mark Noll's "Turning Points" is a great book. It was used in a class I took last year on the History of Christianity, and it was a great resource for looking at the bigger picture, and the idea of history as cause and effect.

Highly recommend the works of Peter Brown, particularly The Rise of Western Christendom in respect to this question. Brown is generally credited with completely re-orienting how historians conceive of the period from c.200-500 (and beyond) and introducing the notion of "Late Antiquity" to periodization. His work offers nuanced understandings of the relationship between Roman culture and Christianization. It also has the advantage of exploring all the varieties of Christian experience around the Mediterranean during the period, because the dude speaks every language ever.

I just started Robert Louis Wilken's The First Thousand Years: A Global History of Christianity. It was very highly reviewed by a colleague in a theological journal, and I've been pleased thus far (admittedly I'm less than 1/4 in). It's not meant to be a very academic read, so he doesn't include footnotes on each page, but it is meticulously researched, and quite intentional about focusing on the whole world. When he narrates an event, he makes sure to highlight what makes it significant, without undermining the reader's intelligence.

I often find histories difficult to read, but this one is holding my attention, and tying together threads that I'd not previously thought of together.

The Cambridge History of the Bible is a pretty in depth, scholarly work.

http://www.amazon.com/The-Cambridge-History-Bible-Beginnings/dp/0521099730

Volume 1 of The Cambridge History of the Bible concerns the earliest period down to Jerome and takes as its central theme the process by which the books of both Testaments came into being and emerged as a canon of scripture, and the use of canonical writings in the early church.

'This volume is a distinguished achievement. Its scholarship is sound and up to date. Nowhere else, it is safe to say, will a reader find so comprehensive and informed an account of the wide field it covers.' Times Literary Supplement

'Once again the editors, publishers and contributors have produced a magnificent volume well worthy to stand alongside its two predecessors ... Judged by any standaed, the History is a landmark in Bible scholarship.' The Evangelical Quarterly

'Professors Ackroyd and Evans have assembled an exceptionally distinguished team for this volume, and the resultant composition is as instructive as it is readable ... Altogether this is an excellent work.' Bulletin of the SOAS

'An indispensable work of reference both for historical theology and for the history of biblical scholarship.' Expository Times Book Description Volume 1 of The Cambridge History of the Bible concerns the earliest period down to Jerome and takes as its central theme the process by which the books of both Testaments came into being and emerged as a canon of scripture, and the use of canonical writings in the early church.