I am sure I am not alone in being intrigued by the work of Max Richter. I was interested without being overwhelmed by his reworking ('recomposition') of The Four Seasons, but the more I hear Sleep the more impressed I am by it.
It's 8 hours long in its full version (although there is a version of a more manageable length on DG) and is, without putting too fine a point on it, designed to put the listener to sleep. For obvious reasons, I haven't heard it all yet (this isn't music to listen to when you're tired, believe me), but within the soporific constraints he's set himself, there is some extremely intelligent work to get to grips with.
Just a shame it'll probably be some time before I manage to hear the entire thing.