Finally. Months and months of hard work:
"This is just an update on progress of our book on Evidence-based Endocrinology. As you may know, thanks to your prompt submission, we were able to meet the publisher's deadline with 100% of the chapters. Just received word from the publisher, Humana Press, that the book is going onto production and that proofs will be available for review sometime in August.
I will keep you updated on any other information I get from them including target publication date and formal title of the book so that you can add your chapter to your CV.
Thanks again for your important contribution - I think you will be pleased with the company that each of your chapters will keep inside this volume. "
Finally heard from my research mentor that our work has been accepted. And, best of all, this wasn't a paper but rather, a textbook. My first co-authorship in a medical textbook. Although I don't get any royalties, I'm happy things went well. Will await the formal publication in a few months' time.