Subterfuge by Rebecca Cohen

In 1594 the Dark Earldom of Crofton was created by one of the most powerful vampire sires to have walked the Earth. Now, over four hundred years later, Ben Redbourn needs to take his seat at the Vampire Council as the 3rd Dark Earl of Crofton, whether he likes it or not.
Under investigation, Ben has to contend with Senior Warlock Ashley Niven invading his home. But there is more hidden at Crofton Hall than Ashley could have imagined with Ben having a demon valet, an elf secretary, and a werewolf in the archive.
Tempers are raised and sparks fly in all the wrong ways until a spell misfires and the tension shifts in a different, passionate, direction which has Ben and Ashley fighting to ignore their instincts.