“Bro!” begins Headley’s delightful new translation of Beowulf, and from there unravels a tale of heroism and machismo and masculinity that honors the origins of the epic poem while also carrying it forward. There’s an unexpected irreverance and comedy here that elevates the usually gloomy tale into a story as brash and boisterous as the brags told by its eponymous protagonist. “He was our man, but every man dies. / Here he is now! Here our best boy lies! / He rode hard! He stayed thirsty! He was the man! / He was the man.” Indeed.