The Hidden Family — Charles Stross

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.

Miriam, a hip tech journalist from Boston, discovered her alternate world relatives with explosive results that shook three 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.

To avoid a slippery slope down to an unmarked grave, Miriam must build a power-base of her own--with unexpected consequences for three different time-lines, including the quasi-Victorian one exploited by the hidden family.