Dangerous Games by Keri Arthur

The 4th Riley Jensen book was an exotic romp into the world of pleasure and pain.  Women are being murdered in Melbourne; their faces frozen in an ecstatic look.  What thing could kill yet the women be "happy" about it?  Riley, her brother Rhoan and the Directorate are looking for the killer while a killer is stalking Riley.  I really enjoy this series set in Australia.  I actually used pieces of it in an old superhero campaign I ran set in Australia.