Vampire Diaries 3 & 4 – The Fury & the Reunion by Lisa Jane Smith.
The Fury:
Faced with an ancient evil, Stefan and Damon must stop their feuding and join forces with Elena to confront it. But in so doing, they are unwittingly sealing her fate …
The Reunion:
Elena summons the vampire trio once more to unite and challenge their fate. Together they will be called to face the most terrifying evil Fell’s Church has ever known.