A Little R and R - Jacob Gunter - Bog

Rand and Rose live the life of comfort and protection under the roof of their parents, who are renowned warriors. But their life of accommodation is turned upside down when their mother and father suddenly leave as a mysterious and overpowering enemy lays waste to all they know and love.
Rand and Rose must take what untested knowledge they have and journey out into a new and unwelcoming world that tests their skills and family bond. Will they survive a world laid to smoke and ruin? Will civilization return? What is greater than family?