Lauren Gunderson is the most successful playwright you’ve never heard of—if you are a New York theatergoer. She has topped American Theatre magazine’s annual list of most-produced playwrights in three of the last five years and ranked second in the other two, but her work is mostly done by regional theaters. Gunderson’s Emilie: La Marquise du Châtelet Defends Her Life Tonight, for example, has been staged from Maryland to Wisconsin to New Mexico to Australia since it premiered at California’s South Coast Rep in 2009, but is just now arriving Off-Broadway.