An alternative to Kindle would be PocketBook, originally Ukrainian, with its current headquarters in Switzerland, and manufactured in Taiwan. I've used their ebook readers for years now, great stuff.
Apart from Storytel, I also know Bookbeat, but haven't tried the latter. Storytel was good though, reliable, decent selection, nothing special beyond that.
I guess it would take a lot of time to accommodate Mars for trees. More than for algae ;)