If you liked Chime by Franny Billingsley, you’ll love The White Darkness. It has an unreliable narrator, and while not set in a fantastical world, it is set mainly in Antarctica (a world I knew nothing about before this book). There’s also an invisible friend, Titus, strong and invincible, and a madness that makes it feel like fantasy.
Sym is a fourteen-year-old girl who goes on a trip with her Uncle Victor who slowly sheds his fatherly pretenses (or was he always the evil stepfather and Sym just didn’t see it?). The trip begins in Paris, but as soon as Sym’s mom is gone home, they quickly head to Antarctica, a place Sym has read and studied about since she was very young. The trip begins with an eclectic tour group and ends with a dwindling foursome trekking toward the South Pole, where Victor is certain he’ll find a portal to the worlds within worlds. And Sym is the one he wants to stay there. Beautifully written by Geraldine McCaughrean, The White Darkness won the 2008 Printz Award.