I'd wait for the paperback - it's cheaper and the cover is beautiful, featuring a detail of Andrea Mantegna's Triumph of Caesar.

This having been said, when it comes out, buy it. It's very good, very well writen, with a new look at the sources, and it's interesting to see the author's perspective on a number of points which are periodically raised here :-)

I'll come back to it later - and hope to read your opinions as well.