Without information about past performance, there can be no learning. Though this essential role of feedback is a basic principle of psychology, it doesn't yet seem widely understood or practiced in the software industry. Feedback is built into many processes in life, especially those by which one attempts to manipulate the physical world. If I try to thread a needle, for example, I can tell immediately whether or not I have succeeded. We in the software industry are working with a more or less invisible product, yet this very invisibility only heightens our need for feedback.
Projects often outlive the accuracy of our memories.
Even when our memories are excellent, people leave during the project and take their memories away with them. So, in order to capture project learnings, we need to plan, prepare, and practice. One of the best features of Norm's book is how it speaks to an engineering audience in engineering terms, teaching us how to transform what we know about software engineering into social engineering. Project Retrospectives is a strong book, full of strong features that will make it the classic work in this area. As I wrote at the outset, I've been looking forward to this book.