I actually only read novels in other languages than my native. I hardly read anything in my mother tongue, since I solely read to improve my vocabulary.

I am reasonably good in English and German, so I mostly can read those books easily. Once though, I have bought the book Katz und Maus from Günter Grass in both Dutch and German. This guy has a very difficult style, with sentences with loads of, unnecessary, clauses. (Which should be poetic then.) I sometimes even had trouble reading the translation in Dutch. So I read a chapter in German, then in Dutch, then reread the chapter in German, and noted the vocabulary I did not know yet.

Since I only actually was improving my vocabulary I was not focused on how the translation differed from the original though.

I often read English books, but it is only because I can access to English books easier.  I found that reading books in the original languages are better than translated version.

Reading a book in a foreign language could be a great experience. But I think it is effective only for those whose have already achieved a little bit of fluency in target language. Otherwise, it will be a little tiring. In my opinion the best way to try become more familiar with language is reading some news, articles and short publications which are interesting to you.

Przynajmniej mi ciężko jeszcze czytać książki w obcym (np. angielskim) języku. Podoba mi się Twój pomysł z czytaniem jednej książki wydanej w dwóch językach. Różnice między treścią spowodowane tłumaczeniem muszą chyba Ciebie, jako czytelnika często zaskakiwać. 

Pozdrawaim 

Your fluency not necessary depends on how many books you read in your target language. I have read tens of engineering books and maybe more of articles and thesis. But with all of that, I still not very good in English. If you want to improve your fluency then you must read about different topics like technology, sports, novels, short stories and so on and the most important practice speaking all the time.

I read a lot in English, anything goes really. In other languages that I know less well I prefer 

books that are light entertainment, a little formulaic, eg. detective stories. The language is probably not too complex and if there's something that I didn't understand there is a certain predictability that helps to guess.