Cephalopods, the group of molluscs that include the octopus, squid, cuttlefish and nautilus, are some of the most fascinating invertebrates to live in the world’s seas. Especially the octopus is famed for its intelligence and mind-bending acrobatics, being able to squeeze through the smallest hole. There have been some fantastic popular books on cephalopods recently, from William’s entertaining Kraken: The Curious, Exciting, and Slightly Disturbing Science of Squid to several works focusing on the octopus (Godfrey-Smith’s Other Minds: The Octopus and the Evolution of Intelligent Life, Montgomery’s touching The Soul of an Octopus: A Surprising Exploration of One of the World’s Most Intriguing Creatures, which made me tear up in more than one place, Mather et al.‘s Octopus: The Ocean’s Intelligent Invertebrate, and Harmon Courage’s Octopus! The Most Mysterious Creature in the Sea). But, as marine biologist Danna Staaf remarks, what’s been missing is a popular book on the evolution of cephalopods. Having been fascinated with them since childhood, she eventually decided to write Monarchs of the Sea*. All hail the squid!