Besides books like Strong Magic and Maximum Entertainment, both of which are excellent resources, I recommend picking up some books solely on the practice of acting and theatre performance. These books are just as beneficial if you know how to apply the knowledge to your magic work. My two personal favourite are True and False: Heresy and Common Sense for the Actor by David Mamet, and A Director Prepares by Anne Bogart. Both books examine how to create strong, compelling, interesting theatrical experiences. The essay in A Director Prepares about the eroticism of performance is particularly useful.
together with my buddy alexander my dog