The Book of Night With Moon — Diane Duane

Wizards and sorcerers, some cats can cast spells and become invisible. They are the guardians of the Gates, weaving and maintaining the magic threads between realities. But when an ancient evil conquers the mystical Gates beneath Grand Central Station, flooding New York with surreal horror from another dimension, a quartet of feline champions is called to defend the Earth. These four small wizards must walk between worlds, cross the River of Fire, and hunt the Children of the Serpent. And in an apocalyptic finale they will engage in ultimate battle against the Lone Power--a dark force that began untold eons before the creation of mere Man...