One day Barbara Hambly mixed all three of the above and made it work. I love the Asher/Ysidro novels. For a long time there were only the two, but the recent vampire craze saw her publishers willing to put out two more (so Twilight DID serve a purpose ... some of the good writers were summoned back to the genre). James Asher is a former British intelligence agent, now retired from the Great Game and happy to spend his time with his wife Lydia (who he adores even if she does have a tendency to fill their bed with her medical journals) and pursue a far quieter career of teaching philology at Oxford. Until one night he comes home from the University to find a vampire in his house, wanting to hire him to investigate the murders of fellow vampires.
I love (as I said above) these books. Hambly's done a lot of research both into the politics and alliances of the years preceding World War I, and into the vampiric and other folklores of many countries to provide a solid background. Asher uses all his skills from his old profession both to investigate and also to protect himself and his wife while all around him folklore has become reality. Lydia Asher has quite a few skills and resources of her own (her hubby adores her for her intelligence and because she's a determined career woman who got herself disowned for following her dream of becoming a medical doctor), plus she has a professional fascination with the condition of vampirism, seeing it as a disease and wondering about both cause and possible cure. And then there's Don Simon Ysidro: damn dangerous, charmingly courteous, a professional "employer", and quite tragic all at once. The uneasy relationship between the Ashers and Ysidro is interesting ... there's a civilized veneer over their interactions but underneath that the Ashers realize Ysidro considers them a threat to his safety and would kill them without hesitation; they in turn know he's a predator that should be hunted down, along with all other vampires, and ended ... each would sleep sounder knowing the other was dead. And yet there's also a certain respect, something that keeps either party from taking action against the other ... for the moment.
From "Those Who Hunt the Night":
They were nearing the miniature maze of streets near the river where the Hotel Chambord stood; the cold smell of the Seine hung in the air, and already, down the cobbled side streets, the milk sellers were about. Asher studied sidelong the delicate profile, the white, hooked nose and loose thickness of colorless hair.
"You haven't relaxed in three hundred and fifty years," he said softly, "have you?"
"Do you relax when you sleep?"
The vampire did not look at him. "I do not know. We all learn too late that sleep is not the same as it was."
"Do you dream?"
Ysidro paused, and again Asher had the impression he was on the point of being lifted and hurled away by the faint stirring of the wind. A faint flex line of a bitter smile touched the white silk of the skin, then smoothed away. "Yes," Simon said expressionlessly. "I dream. But they are not like human dreams."
The Asher/Ysidro novels (so far) are, in order:
Those Who Hunt the Night
Traveling with the Dead
The Magistrates of Hell
The Kindred of Darkness (being released March 2014!!!)