I've read some of it in Zizhi Tongjian in Classical Chinese, which I am not good at but still can manage to go through with a lot of dictionary help. I was wondering if there were good sources for it that were in English. I've found Medieval Chinese Warfare 300-900 that looked alright, although it definitely focuses only on the military aspects and does not limit its scope to the Sixteen Kingdoms era.
I am especially interested in the second half of the era (from around the battle of Fei River to the split of China into just Northern Wei and Southern Song).
Zizhi Tongjian is a great source of course. But for English language sources, there isn't much in the way of general survey, as there is not yet a Cambridge history of the period. 15 Kingdoms is one of the sub-periods of the time after the Qin and before the Tang which has many names. Northern and Southern Dynasties, Six Dynasties, Warring States - all are part of the same roughly 200-600 CE period. Anyway, here are two nice sources that are somewhat meant to accompany a cambridge history, as they are non-chronological, and deal with various aspects of Six Dynasties culture.
Albert Dein's Six Dynasties Civilization
and
Mark Edward Lewis' China Between Empires
Enjoy!