Yes, they support Russian written books. I have no problem to read the books, but the dictionaries do not work. At least they are not linked to the books such that I can find the word on pop-up. I can also not search the Ru dictionary as I can't write any cyrillic letters.
I guess it's the hack out there that I'm looking for. I'm not high-tech enough to understand everything out there, and the Russian written forums are too complicated. I'm still quite new into the Russian language.