"an introduction to impro theater interspersed with a lot of personal stories" seems like a technically accurate but misleading description of the book to me. I struggle to capture the essence of the book, but I'd add that it shows a lot of insight into creativity, relationships, and the human condition.
You are right, and it is indeed quite hard to describe this book. It is less monolithic, more like a collection of short stories each offering unique insight into a topic.