"Dynamics In Document Design: Creating Texts for Readers", by KarenShriver?
Dynamics is a good book, and a model for other attempts to define an evolutionary change in an old discipline. The book walks the reader through the tools of the "new" technical communication/writing: usability testing, scientific research on font choice and use, effective (as measured by usability or perceptual research) graphic design, etc. There's also a chapter that provides a historical perspective on the field which gives much of the context needed to understand why a book like this is needed.
The book is grounded in practical examples and references to the open literature. A good book.