I'm late to the party, as far as The XX is concerned, but better late than never. If you're not familiar either, check out Crystalized in the following playlist for a brief introduction.
If you enjoy Crystalised, you'll enjoy the entire self titled CD by The XX. It showed up on many Best Of 2009 lists and I can see why. And, yes, despite what my spellchecker tells me, Crystalised is spelled correctly - at least, in this case.