Evidence (Alex Delaware #24) by Jonathan Kellerman

In the half-built skeleton of a monstrously vulgar mansion in one of LA's most glamorous neighbourhoods, a watchman finds the bodies of a young couple -- murdered in flagrante and left in a gruesome postmortem embrace. Though he's cracked some of the city's worst slayings, veteran homicide cop Milo Sturgis is still shocked at the grisly sight: a twisted crime that only Milo's killer instincts - and psychologist Alex Delaware's keen insights - can hope to solve. While the female victim's identity remains unknown, her companion is ID'd as eco-friendly architect Desmond Backer, who disdains the sort of grandiose superstructure he's found dead in. And the late Mr Backer, it's revealed, was also notorious for his seductive powers.

The rare exception is his ex-boss, Helga Gemein, who's as indifferent to desmond's death as she apparently was to his advances. Milo and Alex place her on their list of suspects, but the deeper they dig for clues the longer the list grows. An elusive prince, an eccentric with an axe to grind, an ex-lover and her cuckolded husband -- all are in the homicidal mix spiced with eco-terrorism, arson, blackmail, conspiracy, and a vendetta that runs deep. But when the investigation suddenly veers in a startling direction, it's Alex and Milo who end up on the wrong end of a cornered predator's final fury.