"Making the Software Business Case: Improvement by the Numbers" (Addison-Wesley; ISBN 0-201-72887-7) by Donald Reifer is a book about how to make the business case for improving a software process. The premise of the book is that most software project managers have never been taught how to do cost justification and ROI analysis. This book covers that. Personally, I was a systems manager at the beginning of my career as well as having taken many accounting courses so I was already aware of the material in this book. I think the premise is valid for the majority of the community.
This book is an easy read and full of valuable advise about the process. I would recommend it to anyone trying to justify improving their software process.