The Greyfriar takes place 150 years after the Great Killing of 1870 when vampires rose up from being rumors and attacked humans. They don't do well in the heat so humanity field to the tropics and warmer areas.
Adele is the princess of the Empire Equatoria, which is the remainder of the British Empire and rules out of Alexandria. There is an American Republic in Panama and the Japanese emperor fled to Malaysia.
Adele is set to be married to the great Vampire Killer of the American Republic, Senator Clark. Shortly after, the two empires plan to launch a full scale attack to retake their land from the vampires. Before this happens, she goes on a tour to the border states which are independent to gain support for the upcoming war.
Unfortunately her airship is attacked and she is rescued by a mysterious swordsman who goes by the Greyfriar.
I really enjoyed this book and recommend it. Adele is a capable hero and stands on her own and the relationship than forms between her and the Greyfriar was well done. I did guess who he was before it was revealed. I also thought the world and the vampire society and abilities were well thought out and implemented. I look forward to the next book.