I do not have a huge amount to say about the book, but I have posted a review of Grant's The Emperor Constantine. Though brief, I hope you find it useful.
You voted, and I have already started on Ehrman's Lost Christianities. I am quite sure already that I will have more to say about this one. There are several things I am enjoying about the books, though I am not without critique. I guess that is the nature of book reviews; it is easier to come up with problems with a book if you are more familiar with the subject matter.