Complex sentence: She dropped out of the City College of New York (now the City University of New York) to marry Robert Rossner, a teacher and writer best known as a mystery novelist under the pen name Ivan T. Ross.
Split into simpler sentences: She dropped out of the City College of New York (now the City University of New York) to marry Robert Rossner, a teacher and writer. He is best known as a mystery novelist under the pen name Ivan T. Ross.