The Witching Hour takes place in the same "world" that the Vampire books do, but the Vampires don't make an appearance in it.
Rice only recently merged the two storylines, in Blackwood farm and more finally in Blood Canticle, which is actually the final book in both series.
Witching Hour actually has two sequels, Lasher and Taltos, which, after reading the end to Witching Hour, you'll want to read.
All her character's arcs are allegedly closed out for good in Blood Canticle. She wants to move on to other things, now that she's spent so many years with vampires and witches.
<- Slapping myself in the forehead, lol. I did read that entire trilogy. lol I just think of it as the Mayfair Witches trilogy and forgot the title of the first book.
And yes, it was very good.
I was told a few nights ago that she wrote another like Servant... I cannot recall the name now, but it was one word and started with an R... the only thing I see at Amazon that sounds even close, though, is The Mummy or Ramses the Damned...?