One Grave at a Time by Jeaniene Frost is number six in the Night Huntress Series. The Night Huntress Series is centered on Cat and Bones, both of whom are vampires and are constantly dealing with the bad things that happen to them. Each book is basically a mystery wrapped in the Urban Fantasy genre. I enjoy that the relationship of Cat and Bones has built over the years, and actually progressed. There was never a triad, it was always just the two of them fighting and then loving each other. Each book the couple learns to work together better, and they learn to trust each other.
Please note that the rest of the review (after the break), while containing no spoilers for the 6th book in the series may contain spoilers of the series in general.
Absurdly Nerdly 