I enjoyed Hofstadter's _Le ton beau de Marot_, which is precisely about this question; it studies many people's different translations of one particular obscure poem, and asks what properties of the original should be preserved.
One warning: among the genuinely deep insights, Hofstadter can occasionally come off as smug and self-congratulatory about his own poetic genius. I found this rather off-putting - and surprising since I found the tone of G.E.B. rather more like enthusiastic play.