I am very grateful to the translators who make accessible so many of the books I enjoy, and try to acknowledge this in my TBR reviews. The problem is that I don't know any language well enough to begin to know how good the translation is.
As David Bellos points out in Is That A Fish In Your Ear?, the range of terms available for complimenting a translator on her work is remarkably small.
When book reviews pay any attention to at all to the translation of a translated work.... they (tend to) recycle one of a small set of standard words of praise: fluent, witty, racy, accurate, brilliant, competent and stylish. You would have to comb through a great quantity of book reviews to find any nods towards translators that step outside of this set and its quasi-synonyms. Translation quality evaluation criteria are hard to establish ... critical language to express such evaluations seems even harder to find.
... A translation can't be right or wrong in the manner of a school quiz or a bank statement. A translation is more like a portrait in oils. The artist may add a pearl earing, give an extra flush to the cheek or miss out the grey hairs in the sideburns - and still give us a good likeness.... but the users of a translation, unlike the friends of a portrait's sitter, don't have full access to the model (they would barely need the translation if they did).
.... There's no choice but to trust the translator.