The Uprising by Marc Remus

Synopsis:

Magora is about to fall to the hordes of ravenous Unfinished camped right beneath its walls when Holly O’Flanigan returns to the parallel world for the fourth time. To save the place they have come to love, Holly and her friends Brian, Rufus, and Amanda risk everything on a perilous journey through the dark realm ruled by the evil Duke of Cuspidor. There they find the hidden city of the Woodspeople and a mysterious link to Holly’s Grandpa Nikolas.

When they return to the island of Magora, Holly has some big questions to answer. Will she accept the power the High Councilor Krah offers her? Can she find a way to defeat the Unfinished and save Magora? And most of all, where does she really belong—in the real world or a fantasy one?

Holly is torn between the two, and as the surprises mount higher, and an instructor is killed, Holly learns that nothing is what it seems, either in Donkleywood or Magora.