Complex sentence: Susan Cain is an American writer, lecturer, and author known for her 2012 non-fiction book' and related articles and talks, in which she argues how modern Western culture undervalues the traits and capabilities of introverted people.
Split into simpler sentences: Susan Cain is an American writer, lecturer, and author. Her 2012 non-fiction book' argues that modern Western culture undervalues the traits and capabilities of introverted people.