As there seems to be nobody enlightened enough to understand them, the classical koans are beginning to be translated to death.
First of all, I recommend this old translation of Mumonkan:
http://www.angelfire.com/electronic/awakening101/mumonkan.html
It may not have all the background to the koans, but the koans contain meaning.
I just finished another reading of Mumonkan today. This version I borrowed at the local library, and care was taken to translate it in a way that sought to bring Rinzai and Soto zen together. Most of the koans were correct, but some had their meaning destroyed.
The author sought to bring some background to them in the end, which sometimes brought needed clarity, but if he even stumbled upon the koan meaning, it was by pure chance.
After this, I read The Book of Serenity.
http://www.thezensite.com/ZenTeachings/KoanStudies/Shoyoroku.pdf
These koans were mostly just complete rubbish. I get the feeling that somebody must have used Google Translate.
If I had the time, I would write my own translation of Mumonkan, in an attempt to save zen from meaninglessness.