Having the book content accessible on the Internet while I was writing the book was a great benefit, both to the quality of the book and to my morale while writing it. Keeping the content available even after publication has been a great boost too, so people who don't want to purchase the book can still benefit from it. (I am pleased to see content of the book Practical PostgreSQL, http://www.commandprompt.com/ppbook/, has also remained online after publication.)
Writing a computer book is different from writing a general book because computer books require an excruciating amount of detail to convey information to the reader. It is easy to see why this is the case. Most items people use in their daily lives perform a limited number of functions. A dishwasher, a television, and even a car perform only a few basic functions and are fairly limited in how they can be controlled by the user. Certain devices, like VCR's, stretch the capabilities of their users, e.g., programming your VCR. Computers in some ways are alone in their ability to morph themselves to perform almost limitless functions. Of course, the computer doesn't move or make toast, but the input, processing, storage, and display devices can be manipulated in an infinite number of ways to perform a variety of functions. It is this open-ended nature that make computers so powerful, but it also makes them complicated to control.
In writing a computer book, it was my goal to take the limited topic of PostgreSQL and present it in a way that would make its form and function clear and controllable. Though I required the software be installed (more on that later), I did not make any other assumptions, and this allowed me to coherently present PostgreSQL's capabilities. The trick was to make PostgreSQL's capabilities, even the complex ones, almost obvious to users with no previous database experience.
In fact, one great challenge of the book was to order items in a way that there were few forward references to material that appeared later in the book. Another challenge was deciding what not to mention, or perhaps mention later, for fear that it could confuse readers more than help them. I also found the writing process to be similar to the process of programming enhancements to PostgreSQL -- my first attempt usually gets the job done, but is far too large and unorganized; my second attempt is closer but still doesn't fit cleanly into the existing code; and my final patch is usually the smallest, slipping into the code as though it was meant to be there all along. In writing my book, my goal was to fit together the pieces of PostgreSQL with the same clarity that exists in our source code.
Anyway, that was my goal, and I think I was fairly successful. However, this emphasis probably surprised some people. Most computer books fall into several general categories:
Writing an open-source computer book is also slightly different from a general computer book. Open source software, and particularly PostgreSQL, is rapidly changing thanks to the many talented developers around the world connected via the Internet. However, a book, once printed, is hard to change, so care must be taken so the book remains relevant long after printing. The delay for translation into other languages makes longevity even more important. By placing reference material into a separate section, users can easily refer to it while reading the book and they can refer to more current reference material when future PostgreSQL releases are made. This is also why I did not cover installation in detail in the book -- PostgreSQL installation changes in subtle ways from release to release, so rather than provide material that may fail to work in future releases, I felt it was better for people to refer to installation instructions that exactly match the PostgreSQL version they are using.
The book is now in its third printing. The number of errors were minimal, thanks to the many reviewers of the online version. I continue to update the book's web page, http://www.postgresql.org/docs/awbook.html, with changes relevant to PostgreSQL releases and with additional chapters. I am glad people are enjoying it. Writing a book was a great experience for me, and maybe someday, I will do it again.