We Sled with Dragons — C. Alexander London

The Navel Twins are at it again, for the fourth and final time! This time their travels take them to the North Pole where they are forced to sky dive, go dog sledding, get rescued by a man in a hot air balloon who looks vaguely like Santa, and finally find the long-lost Library of Alexandria. If they can get through that, they might have a fighting chance at finally going back to being couch potatoes. But that's a tall order for the world's most unenthusiastic siblings.