And if you travel a lot and invest in a BahnCard 50, long distance trains are not that expensive anymore. A Flex ICE ticket from Nuremberg to Hamburg will cost you 80€. Fuel will be more expensive. Well, if you buy the ticket a week earlier, you can get it very cheap like 13€.
You can install KOReader on Android as well. Well it lacks OPs material Design requirement, but it fulfills the other.