Lynne Tillman’s unnamed narrator in American Genius is a geyser of talk. Stuck in a New Age colony for scholars, she holds forth on cats, skin rashes, and her fear of overflowing toilets. She’s a flotilla of neuroses à la Woody Allen, given to free association: ”It’s the wild stallion, the uncapturable horse, I cherish…” While such asides are initially irritating — where’s the plot, the dialogue? — Tillman’s prose builds to poetic brilliance. Here is a mind folding in on itself. ”My second heart grinds with nameless worry,” she pleads, ”ungracious doubt rumbles in my intestines.” As she sadly discovers, logorrhea is the symptom of her problems, not the cure.