Mark Birkey is an Associate Director at Random House Production Editorial at Penguin Random House. He handles copy-chief duties for the Crown imprint and leads a team of seven production editors. Twenty-plus years ago, Mark began freelance copyediting because of the flexibility it offered while pursuing a music career. Since then, he’s worked as a copy editor, proofreader, or production editor on books by Trevor Noah, Matthew McConaughey, Rachel Maddow, Patti Smith, Erik Larson, Timothy Snyder, Susan Cain, Anthony Marra, and many others. Mark is a big fan of the serial comma.