In their description of spiritual literacy, Frederic and Mary Ann Brussat write that the first step in the practice of mystery "is to cherish the baffling, curious, hidden, and inscrutable dimensions of your existence and the world around you." Children live closer to this practice than most adults do. They recognize that in the dark, something might be hiding under their bed or in the closet. They have imaginary friends we can't perceive. They ask an endless stream of why and how questions, many of which we can't adequately answer.

Books that allow children to explore the boundaries between the known and the unknown hold a special place in their lives. Ben Hubbard, an accomplished nonfiction author for children and adults with more than 130 titles to his name, brings us this marvelous volume about the Kraken, a multi-armed sea monster greatly feared by seafarers for thousands of years.

Hubbard regales 8-to-12 year old readers with historical stories from sailors who recounted struggles with these creatures. He describes contributions to the Kraken myths from Homer, Tennyson, Jules Verne, and Herman Melville. He reveals scientific discoveries with engaging detail. For instance, one giant squid that washed ashore, allowing for in-depth study, had tentacles "twenty-six feet in length. That's about as long as a school bus."

Side notes address topics like Greek Mythological Monsters, the Hafgufa (a giant sea monster from Viking lore), and the 2010 internet meme "Release the Kraken!" Throughout the book, Robert Squier's black-and-white illustrations pull children into the worlds of the creatures, ships, museums, explorers, authors, and scientists mentioned. We appreciated his depictions of women whenever possible — as scientists, teachers, and museum curators — since the older tales passed down to us involve only men.

The book answers lots of questions but leaves readers with their sense of mystery intact. Acknowledging that 95 percent of the ocean is unexplored and only 10 percent of creatures have been scientifically classified, Hubbard writes, "Who knows what ancient creature ... remain hidden and undiscovered? Perhaps the Kraken is not the colossal or giant squid but an even older, larger creature waiting to reveal itself."