The Crosstime Traffic series is an interesting premise on alternate histories. In the 21st Century people go back in time to trade with the locals for food stuffs or other supplies needed in the 21st Century. Or on unpopulated worlds you can mine for minerals and oil without worrying about harming the ecosystem. Jeremy and Amanda Solters’ parents are traders from the 21st Century working in the Roman Empire. They trade pocket knives and straight edge razors for grain. Jeremy and Amanda join them over summer vacation. Until one summer, Jeremy’s mom becomes ill and has to go back to the 21st Century for medical care leaving Jeremy and Amanda to fend for themselves. Unfortunately, a war breaks out with the Lietuvans. Will Jeremy and Amanda ever get back to their own time?