The series starts with Halfway to the Grave and to be honest, the tale isn't really concluded in the first novel. If you're in for Halfway to the Grave be ready to take on One Foot in the Grave to finish the initial story line.
Subsequent series spin offs include books about Spade and Mencheres, and various other characters (vampires) you meet as you go along. Supposedly Vlad one day soon. But it lost the magic for me.
But don't discount the magic of the first two books! Oh baby! They're worth it!
After the first two or three novels, the series starts to suffer from having too many too powerful (or all powerful) characters. First it was flight. At first the reader didn't know that vampires could fly, but they can do that. Now you always have to wonder hey, why didn't they just whoosh there? Now the author (and consequently) the plot, faces huge challenges from having vampires who can hear the goings on in buildings quite a distance away -- and therefore can spy on each other from that distance -- as well as telepathic abilities which keep being granted to more and more characters.