In scriptwriting, when characters say what they mean, that's considered "on the nose" - or the text. Dr. Seger urges writers to go deeper, using the subtext (or the deeper meanings to what characters are saying - their words are not taken at face value).
The main part of the book is split into 6 chapters (there's also another writer's perspective on subtext, and an afterword). After exploring in detail what exactly she means by subtext, Dr. Seger then gives writers a number of ways to bring subtext into their own writing (through characters, words, gestures, similes/metaphors, and through genre). It's a very thorough examination of the topic in such a small book (I read it in a day, although I did not do the exercises that were included at the end of every chapter). Writing Subtext was a very good book that I'm glad I read - it's really given me a lot to think about in my own writing!
