Liminal Key

Krystal Fisher is a neglected American housewife writing novels to make extra money for her farm, and her husband. When she's Magicked out of her backyard by two mischievous Elf toddlers, Evan and Inga, to an Alternate Earth, called Niflheim, or Ice Home; planet of mist that orbits a Cold Black Sun in a Hot White Universe filled with Black Stars. She unknowingly promises to marry their father, an impossibly seductive and strong Elf soldier. The flora, fauna, Fairies, and humans feed off of the Cold energy from the Black Sun, but it is fatal for all Elves; they must hide underground or they will age rapidly and die a painful death from exposure.