I know Greg posted below about Christopher Boucek's Carnegie piece, but having read it last night I want to doubly endorse it. It is a large overview, but unlike many large pieces it hones in on many key and often over-looked details. One I found particularly interesting was the amount of private wells in the country, which points to how corruption is exacerbating the ecological catastrophe that is about to overwhelm the country. The entire paper is full of things like this, but it also never misses the forest for the trees (Friday is cliche day here at Waq al-Waq). Boucek also demonstrates how impossible it is to try to solve on of Yemen's problems without addressing any of the others. So, I know this is redundant, but I can't recommend it enough.