It’s Sunday, which means it’s time for another big Kindle ebook sale. Today, the focus is on biographies, historical nonfiction, and business books. Brush up on your public speaking skills, learn about the influence of drugs in Nazi Germany, or enjoy memoirs from Gabrielle Union, a longtime White House chief usher, or, uh, the Property Brothers. Most of the books are only $2 or $3, so get to downloading.