Friends of mine who had been familiar with Boswell's first book, 'Christianity, Social Tolerance, and Homosexuality', from its initial publication in 1980 waited impatiently for the follow-up volume. In the end, it took fourteen years to produce, and sadly, did not live up the expectations that had been given it.
Firstly, it did not in fact reveal (if such places exist, the not-always-so-hidden charge behind the disappointment) communities that had continued the practice of tolerance to same-sex couples through the last millenium within the structures of Christendom.
For part of the book he covers old ground, talking about the milieu of the Greco-Roman world, and talks about the development of the idea of marriage and liturgical practices for that. He then proceeds to give examples of liturgies which, Boswell claims, are proof that the church did recognise and bless same-sex unions. This claim is still debated, as there is no blantant 'I now pronounce you husband and husband (or wife and wife)' kinds of statements or liturgies here, but rather testimony to friendship, companionship, communal support, of a sort that is ambiguous.
While this book is important for liturgical forms and narrative discussion (although the narratives can be reinterpreted as something different from Boswell's), it failed to deliver the knock-out punch readers of the first book had been waiting for, i.e., conclusive proof the church was up to no good. Boswell does make some points worthy of attention in the debate, such as, 'The extent of early Christian hostility to same-sex eroticism has been exaggerated by modern Christians, who tend to overlook comparable Christian strictures against divorce or other common aspects of modern life also condemned by the early church, while focusing their energy and moral outrage on this particular issue.'
Boswell is interesting but far from satisfying on either side of the debate. So, after providing us with some historical framework, we must move on to more explicitly theological discussions. Boswell's contribution is an important one, in that it shows that this has been an issue with varying degrees of acceptance and controversy throughout the life of the church, and the history of society in general. It does not, however, settle anything, or satisfy either side -- it is rather more grist for the mill for both sides. An important book, but not definitive by any means.
Unfortunately, Boswell died not long after the publication of this volume, and so further clarifications, or any unpublished research of sensitive nature, will not be forthcoming.