It's a bit of both! The Witching Hour and Taltos are set mostly in the present, although you get the history of the family in TWH so it does go back in time a bit, and the middle book, Lasher, tells you the story of how Lasher was formed and of all the generations of witches so although some of that is in the present there's also quite a lot in the past too, if that makes sense.
I agree that Anne Rice can be a bit erratic, I have all the Vampire Chronicles as well but some of them (especially around the middle of the series) do go off a bit and are quite boring, but the first few and last few are great, I love Lestat!
