Trolls in the Hamptons - The Willow Tate Series, #1

Willow Tate is a graphic novelist who earns just enough money at her craft to keep he rent-controlled Manhattan apartment and still put food in the refrigerator. Then she decides to write about a troll who's a superhero - and one suddenly appears, causing mayhem in Manhattan. The odd thing is that nobody except Willow can actually see the stony red giant. Willy thinks she's going crazy just like her grandmother did, until she meets handsome, sophisticated, and oh-so-British Agent Grant from the Department of Unexplained Events.
According to him, Willy has managed to break ages-old cosmic laws that could destroy the world as we know it.  Now she has to help him save the planet, rescue a little boy, and find a murdering kidnapper who wants to use the power of a small village in the Hamptons to become master of the universe. Along the way, Willy discovers that trolls don't deserve their bad reputation, that she's not the only person in the town of Paumanok Harbor with special talents, and that magic and true love really do exist.