A sad sad book
This is a sad book - a sad sad book, as the people of Eden would say. They are the 500 or so descendants of two explorers who were marooned in a strange land with no sun, only a dim light produced by plants. Because there was necessarily inbreeding, some of them have deformities: claw feet or ?bat faces?, and many die young.
They live as one family in the forest, following certain laws, revering their memories of Tommy and Angela and waiting for Earth to come for them.
When John tries to explore Eden, to expand their hunting and foraging space, and cross the snowy mountains to find new places to live, it upsets the balance and brings conflict within the family.
Eventually they find remains indicating that there is no hope of rescue from Earth, so they are on their own, and will have to work out for themselves things like ?lecky-tricity? and waterproof clothing.