Neverthorn by Shannon Mayer

In a realm where magic reigns, a legendary Hero once stood against the encroaching darkness. But with his death, hope dwindled, and the best the world can muster is Harlow Daygon—a thief, magic school dropout, and notorious troublemaker.

At nearly thirty, Harlow can’t even cast a simple rune without blundering it. So why does anyone think she can take up the mantle of Hero? Reluctantly, she’s dragged back to Neverthorn Academy with seven former classmates, tasked with training to confront and defeat the Villain of their world.

But the challenges are stacked against her:
Professor Hot-As-Sin makes it clear she’s a failure.
Professor Used-To-Be-A-Mean-Girl has a vendetta.
And lurking in her past is a secret so dark it could reveal she’s not the Hero the world needs—but the next Villain.
With fate hanging in the balance, can Harlow embrace her destiny before the shadows claim her?