Cressida's Agents - Empire of the Sky, #3

Replete with all the trappings of an alternate world -- airships, steam powered aircraft, automatons, moon bases, and witches with psychic powers -- Cressida's Agents is a steamy thrill-a-minute ride in a universe of what could have been. Cressida Troy, after being mesmerised into betraying humanity, is now the wife of Mon Ilson, the alien leader, and is crowned Empress of Space. While pretending to be the love of his long-life, Cressida is desperately seeking a way to redeem herself, and somehow save human civilization from destruction at his hands.
Then her former fiancé, Jacob, is captured and brought to the moon. Can she earn back his love, or has her seeming betrayal hurt him too much? Meanwhile on Earth, Marjorie, in the guise of brothel madam and casino owner is acting as an agent of Mon Ilson. Her goal is to learn from him the secret of immortality, and for now she must do his bidding. A violent assassination attempt on her airship Fortuna brings her into the strong arms of handsome Squadron Leader, Sir Christopher "Kit" Colby.
Her attempt to uncover the mastermind behind the plot leads them both into deadly danger.