The Hidden Family by Charles Stross is the second instalment of The Merchant Princes series - an energetic saga of parallel worlds.
The six families of the Clan rule the kingdom of Gruinmarkt from behind the scenes, a mixture of nobility and criminal conspirators whose power to walk between their world and ours makes them rich in both. Braids of family loyalty and intermarriage provide a fragile guarantee of peace, but a recently ended civil war has left the families shaken and suspicious.
Miriam, a hip tech journalist from Boston, discovered her alternate-world relatives with explosive results that shook the worlds. Now, as the prodigal Countess Helge Thorold-Hjorth, she finds herself ensnared in schemes and plots centuries in the making. She is surrounded by unlikely allies, lethal contraband, and, most dangerous of all, her family. With her modern American attitudes, she's not sure she can fit in, or if she even wants to, but to stay alive, she really has no choice . . .