Dark times - Christopher Golden

When Buffy wakes up in what appears to be an alternate future, she is appalled to discover that evil has overrun Southern California and that vampires rule. Her friends have rallied to fight a rearguard action against the new order - but they are very different from the friends she thought she knew. Willow is a fully-fledged sorceress, Xander a battle-scarred, humourless veteran, and Oz a frightening split personality. But what shocks Buffy most of all is that Faith is gone, all her bravado unable to help her, and a new Slayer has been called in her stead.
Back in the present, Buffy's friends are puzzled by her behaviour, unaware that the Prophet inhabits her body. Either they are going to have to find a way to bring her back to them, or Buffy herself, trapped in her dark future, will have to find her own way home -- if she can overcome the nightmare that awaits her.