This book has much to recommend it, but it is more of a compendium of a great of deal of research by many scholars - an attempt at an overview of the field - more than it is a history book with its own set of arguments and archives. In this way it is something a bit more akin to Ruth Mazzo Karras's Sexuality in Medieval Europe than it is to Boswell's Christianity, Social Tolerance, and Homosexuality. Crompton is attempting to bring together work such as Guido Ruggiero's writing on Renaissance Venice, Kenneth Dover's writing on ancient Athens, Michael Rocke's work on Florence, and numerous other people's work.
Crompton's own interest is in legal history - where the preponderance of documented evidence about homosexual behaviors seems to be found. (Even the small sections on the Mayans, the Aztecs, the Inca, and the Chimú are focused on the ways they legislated same-sex sexual activity.) I would say that his secondary interest is in literature and memoirs. What this book is not is a social history. Crompton's focus is on the intersection of anti-sodomy legislation and those who found themselves subjected to those laws. Homosexuality and Civilization is, in many ways, designed to be a correction of Boswell – whose work downplays anti-sodomy persecution. Crompton is interested in documenting anti-sodomy hostility and persecution as a way to call European civilization, Christianity, and even the Enlightenment to account for the carnage and violence they wreaked.
Frequently Crompton does come to the question of whether or not a homosexual subculture might have existed in this or that oppressive locale – Florence, Venice, Paris, London – but his results here are often inconclusive or say nothing about how these folks who frequented particular sites for homosexual sex might have understood each other or what they were doing. And then because the book is such an enormous survey of activity, Crompton doesn't really have the space to interrogate these questions in any depth; he tends, simply, to move on to his next topic or location.
In short (even though the book is quite long) this is an accessible, moderately in-depth overview of the history of homosexual laws and literature in antiquity, the medieval period, pre-Meiji Japan, Imperial China, the European Renaissance, and the Enlightenment. Much of the world makes no appearance at all, and Crompton's chief focuses are, on the one hand, oppression and anti-sodomitical violence, and on the other, kings, queens, emperors, shoguns, generals, and other powerful people whose same-sex relationships are well documented.