“DO YOU KNOW how a river forms?” is the question that begins Houston author Vaishnavi Patel’s new book, Goddess of the River. The voice belongs to Ganga, goddess of India’s Ganges river, who has been transformed against her will by Lord Shiva from “a tributary of the cosmic ocean” into the physical form of a mere winding river, with no path to the heavens, only the sea. Later, Ganga runs afoul of a powerful sage who transforms her yet again into a human, and as it happens in myths, things get complicated.