This question is best answered in the preface. Let me repeat the relevant portion here since this question is quite a FAQ.

After working on, programming on, and extending several operating systems over the years, I was introduced to Mac OS X on April 1, 2003. I was soon curious about the structure of the system. Despite the availability of several good books on Mac OS X, I was dismayed to find that I could not learn the details of Mac OS X internals from a book—no such book existed. Although the existing books play important roles in making Mac OS X accessible, the core architecture and implementation of Mac OS X and its components have remained mysteries. To make matters worse, besides the lack of information, it is common to find misinformation on the composition of Mac OS X. Consequently, the system is often misunderstood because of long-standing myths and stereotypes, or is perceived as a black box.

Therefore, I wrote this book to deconstruct and demystify Mac OS X by describing it from a system-design perspective. I used an implementation-oriented approach to explaining the system.

This is a somewhat complex question to answer accurately, but the short answer is "about two years, with a year-and-a-half of active writing." I wrote the book in my spare time, while I had a full-time job at IBM Research. (Yes, it was not easy.)

I was first approached by Addison-Wesley in January 2004, shortly after I published an online document called What is Mac OS X? on my personal web site kernelthread.com. By the end of February 2004, I had signed the book contract. I officially began writing the book on March 1, 2004, and officially finished on November 8, 2005. During this while, I spent most of my free time on the book, barring a two-month period when I did not work on the book at all for family reasons. Since the book took so long to publish after I had submitted the manuscript, it was never really "finished" because Mac OS X is such a fast moving target—I kept revising the manuscript long after November 2005.

I drew the illustrations using Adobe Illustrator.

I created osxbook.com as the book's accompanying web site. I briefly considered using kernelthread.com, my personal web site (which I also created) to serve the book, but decided it would be better to have a book-only site.

I sometimes use Macromedia Dreamweaver to apply site-wide template changes, but most content is just written using the vi editor. The site uses phpBB as its forum software, WordPress as its blog software, and traces of JavaScript and PHP otherwise.