The novelization of the animated film, written by Pennac, based on children's books about the friendship between a mouse and a bear by Gabrielle Vincent. Pennac envisions the story of how Ernest and Celestine met, turning this into a political fable of consumer capitalism versus totalitarianism, a 'Cold War' of sorts. Initially, the big bear Ernest and Celestine the intrepid little mouse live on the same planet but in different worlds. In the greedy aboveground 'bear world, ' Ernest wants to sing instead of grow rich by selling candy to children and then fixing their decaying teeth. In the industrious rodents' totalitarian underground city, the individual does not count, and everyone is obsessed with maintaining their incisors, in fear of the 'great bear villain.' Celestine works for the Great White Dentist Clinic, collecting milk teeth from the aboveground world -- but she only wants to draw. The film is also a beautiful fable about the meeting of two artistic vocations: on one side, a bear who dreamed of being a musician; the other, an unfortunate little mouse who is obliged to become a dentist while she thinks only of drawing. One day, Ernest discovers Celestine hiding in a dumpster in his world. His first instinct is to eat her, but soon they become inseparable, linked by their artistic natures. Aadvocating tolerance, they help and support each other. Together they undergo many adventures: they must escape the police from both above and below, and hide and defend themselves from intolerant natives of both worlds. They end up being tried in the separate courts of their worlds, where they are judged on appearance and social status (bear, mouse). Nonetheless, all will end well for both companions.

"A tender and funny novel, rhythmic and joyful. A beautiful story of friendship which shatters preconceptions."--Https://lesmotsdelafin.wordpress.com/2013/09/13/le-roman-dernest-et-celestine-daniel-pennac.