I agree with the favourable reviews already here - this is a very good album. I hadn't heard any of The Civil Wars' music until now and am very impressed.
There is a lot of quite-good-but-not-brilliant Country/Americana around, and this stands out from the crowd for two reasons, I think. The first is the quality of the songwriting. These are largely songs on the age-worn themes of love and loss, but they have an unusual lyrical depth and are musically very good with a great variety, singable melodies and, I suspect, a lasting quality.
The second reason is the exceptional quality of the singing. Both Joy Williams and John Paul White have very good voices which contrast rather and combine wonderfully. They can both really belt out a tune when needed, but also sing the quiet, tender passages with real feeling and exceptional skill. It reminded me slightly of the best moments of the Robert Plant/Alison Krauss collaboration. The production is admirably restrained and doesn't immerse the material in slick gloss, which allows the quality of the singers and their songs to really shine.
I'll be getting hold of Barton Hollow very soon on the strength of this. I warmly recommend this album - it's a bit of real class, I think.