I am reading a really excellent short book by Morna Hooker and Frances Young. Called Holiness & Mission: Learning from the early church about mission in the city (SCM), it consists of the Hugh Price Hughes lectures delivered in London earlier this year.
Hooker and Young, colossi of New Testament and patristic studies respectively, write two chapters each dealing with their specialism and then a joint chapter drawing lessons. It's wonderfully erudite, concise and yet chock-full of information and insight.
I wish it had been available six months ago when I was mapping out my MA because it would have helped me shape the argument. It covers not just the NT period but the sweep of early church history up to and a little beyond Constantine. I strongly recommend it. It's made me want to read more by Frances young.