I picked up a copy of Augustus Richard Norton's new short history of Hezbollah the other day, and so far, it's pretty good. I'm only on the second chapter, but from the little I've read, it's pretty solid. Although one thing is certain: at 159 pages, it certainly is a short history.
Here's a piece of trivia that I didn't know: in the late 80s, when Amal and Hezbollah were fighting, Nasrallah's brother Hussein (who is a fervent Amal partisan) was actually on the front lines fighting against Hezbollah.
Otherwise, here's an NPR interview with Norton available for streaming.