Slippery BeastA fascinating account of a deeply mysterious creaturethe eelmixing true crime, natural history, travel, and big business. Ellen Ruppel Shells Slippery Beast is a captivating exploration of the enigmatic eela thrilling saga that weaves together elements of true crime, natural history, travel, and big business. What is it about eels? Depending on who you ask, they are a pest, a fascination, a threat, or a pot of gold. What they are not is predictable.