Moustetronaut is a lovely picture book by Mark Kelly, a former Space Shuttle pilot and husband of former Congresswoman Gabrielle Giffords. It tells the story of Meteor, an experimental NASA mouse who saves a shuttle mission by scurrying into a tight control-panel seam and retrieving a critical lost key. The story is very (very) loosely based on a true story -- there was a Meteor, but he never left his cage, but he did indeed display delight and aplomb in a microgravity environment. The whole rescue thing is a fiction, albeit an adorable one.
What really makes this book isn't its basis in "truth," but rather the amazing illustrations by CF Payne, who walks a very fine line between cute and grotesque, with just enough realism to capture the excitement of space and just enough caricature to make every spread instantly engaging. There's also a very admirable economy of words in the book itself (which neatly balances a multi-page afterword about the space program, with a good bibliography of kid-appropriate space websites and books for further reading). It's just the right blend of beautifully realized characters -- Meteor is particularly great -- and majestic illustrations of space and space vehicles.