The final novel of the "Ghost" Trilogy by Mr. Modesitt, Ghost of the White Nights is cunning. Set in an alternate universe, Doktor Johan Esachbach, a former Spazi spy and Professor of Environmental Science, and his wife - the world renowned singer Lysette, head to Russia for adventure.
The world is very different: the greater part of North America is the Dutch-English country of Columbia; France is part of Austro-Hungary, and Russia is still ruled by the Romanovs.
Though the two would be more than happy to be left to a quiet life of teaching (and singing for Lysette), the Columbian government cannot afford to leave Johan and his wife in peace. Lysette is sent on a cultural exchange mission to St. Petersburg where she is to sing for the Tzar. Johan is to accompany her, of course, and work behind the scenes to force a settlement between Russia and Columbia for desperatelt needed oil.
Unfortunately, it is not quite that simple, and Johan discovers a plot involving a deadly weapon in the works, more powerful tha the nuclear devices of Astro-Hungary.
Ghost of the White Nights is a well done alternate-reality tale on par with the work of Harry Turtledove. Johan reminded me of a rather Dutch-pseudo American James Bond, with all the flare of the well-known fictional spy. For both science fiction and espionage novel fans, this book is a definite must have, and is recommended by this reviewer with a whole heart.
Title: Ghost of the White Nights