Coleman Barks is a translator of the poetry of Moulana Jalaluddin Rumi, a Middle-Eastern mystic and ecstatic poet in the Sufi tradition of Islam.
Barks's translations might more accurately be called "versions," because they are much more free interpretations of Rumi's work than most. He has come under criticism for his work because some scholars feel that his versions do not accurately relay the poetry of Rumi. This is partly because Barks does not know the original Arabic (and therefore uses multiple existing translations as his sources), and partly because he actively sets out to convey the meaning of the poetry rather than the diction.
Barks's versions are excellent for casual reading, I have found, but if I were to do serious study of Rumi's poetry, I would use other sources in addition to, or perhaps in place of, Barks.
Sources: memory of introductions to a couple of books of his versions.