Books in the Puck the Magic Penguin series

At the end of the Adventure of the Pink Ruby (book 2) Puck uses his magic to transport Nef and her friends to Puckovakia, a land 150 years behind ours. There are no phones, TVs, or computers. The group is escorted to Queen Nya, and learns that Puckovakia has become divided between the Highlands and the Valley due to the corruption of the Valley leaders. Because of their corruption, Notwat Island, which sits in the middle of the river on which almost all trade flows in and out of Puckovakia, is now controlled by the evil Johnson. The adults have seriously messed things up and it's up to Puck and the kids to make things right.