The Shadow Princess — Mary Hart Perry

As Jack the Ripper terrorizes London, Queen Victoria's daughter is drawn into the case in this romantic historical thriller.
 
1888: A year after Queen Victoria's Golden Jubilee, terror mounts in the city's slums. A killer has butchered two prostitutes, the crimes brutal even by London's hardened standards. Rumors of the murders reach Princess Vicky, daughter of Queen Victoria and grieving widow of the German Emperor Frederick III. When her niece Princess Maud visits, she brings with her even worse news: The Metropolitan Police have a suspect. It's Vicky's nephew, Crown Prince Eddy. Desperate to clear her family's name, Vicky rushes back to England.
 
Det. Inspector Thomas Edmondson believes there is a royal cover-up behind the killings. He will stop at nothing to expose the truth and bring a murderer to justice before he can kill again. But when Vicky joins him in searching for the man who will become known as Jack the Ripper, neither of them foresee the overpowering attraction that will draw together the royal and the commoner -- or the danger their love puts them in.