Story: Substance, Structure, Style, and the Principles of Screenwriting
Yes, this is a screenwriting book. However, we've found it to be one of the most comprehensive books written on storytelling (which is absolutely crucial to the Dad's style of improv). Story is a great resource for learning the ins and outs of scene structure, character arcs, and genre. This should be especially of interest to those of you interested in long form improv.
By Robert McKee