I found it to be a really brilliant introduction to Christian sexual ethics. Mostly because the writing is just stellar - really clear and easy to read, without sarcificing any nuance.
The book is largely non-polemical, providing an introduction to several key ideas throughout the history of Christian sexual ethics. Where there is a larger argument of the book it is to argue two premises:
1) In the Christian tradition, sexual identities have largely been considered more important than sexual acts within themselves.
2) The Church and state have throughout the majority of Christian history been partners in policing human sex, and that this is now an area that has become the responsibility of the state - and that this was a more fundamental shift for Christian sexual ethics than such events as the sexual revolution.
To me the second premise felt to be better argued than the first, but to really make a call on this, much deeper study would be required.