The approach that this book takes is to present an idea eg "The Inner Backstory Defines Character". There's an all-too brief discussion, then possibly some reports of what Freud, Jung, and/or some other lesser-known writers might have said to support the idea, and then we're into the case studies.
I have to admit that this approach is not really my cup of tea. I want to get to the meat that the author has to offer, and avoid the flabby case-study filler. Perhaps if it was written in a more engaging way, I might feel differently, but as it is, I'm tempted to skip long tracts looking for the useful bits. At least the summaries at the end of each chapter help in this - I quickly concluded that the book would be more useful as a set of reference cards pasted up from the introduction to each idea, and these summary pages.
I'm currently reading "Characters and Viewpoint" by Orson Scott Card, and thinking comparatively about the two books is what prompted me to write this review. I'm finding Card's approach to be far more engaging and usable. Even his section headings are directly informative, as opposed to the simple descriptions used in Seger's book.
In short: check the Card book out before making a decision on this one.