Since KMA's biography of Zhang Jue doesn't really give us a scope of historical background of this chap, I dug out a very detailed one from Gongjin's War Memorials which has, at least for me, served to give more weight and depth to this enigmatic figure:
http://threekingdoms.wikia.com/wiki/Zha ... 5%E8%A7%92
An excellent read, for anyone interested in the origins and mindset of the Zhang brothers and their attempt at a serious political and military coup.