YemenYemen is the dark horse of the Middle East. Every so often it enters the headlines for one alarming reason or anotherlinks with al Qaeda, kidnapped Westerners, explosive population growththen sinks into obscurity again. But, as Victoria Clark argues in this riveting book, we ignore Yemen at our peril. The poorest state in the Arab world, it is still dominated by its tribal makeup and has become a perfect breeding ground for insurgent and terrorist