The Fates. Coven, #14

Everything happens for a reason. The Fates pay Samantha and Kathy a visit when the sisters' misstep, which left a man the target of a vampire bite, leads to unimaginable consequences in the future. Unconvinced of the effects of one bite, the sisters travel forward to the future, where, at first, everything seems perfectly normal.until nightfall when the world seems to plunge into dystopia. Soon, the sisters find themselves on the run from a vampiric empire taking over the city, and possibly even the country, as they uncover terrible truths about their future.
With their efforts to return to their time having failed, the sisters fear that they may be stuck in the horrific future that they've inadvertently created. The Fates is the fourteenth and final book in the Coven series, which is part of the Art of Magic universe, containing the Lost By Magic and the Under the Moon series.