The House at the End of the World by Dean Koontz

In retreat from a devastating loss and crushing injustice, Katie lives alone in a fortresslike stone house on Jacob's Ladder island. Once a rising star in the art world, she finds refuge in her painting.

Katie soon finds herself in an epic and terrifying battle with a mysterious enemy. But Katie's not alone after all: a brave young girl appears out of the violent squall. As Katie and her companion struggle across a dark and eerie landscape, against them is an omnipresent terror that could bring about the end of the world.