There aren't many worthwhile things to read if you want to know more about Developer Studio customization. Your first option, of course, ought to be Microsoft's documentation which is available with DevStudio itself, and through the Microsoft Developer's network (MSDN) channels. There, you can find a full description of the object model, as well as a reference for VBScript—which is the only language supported at the moment.
However, the official documentation is often discursive and not enriched with insightful samples. A good support for it is an article which appeared in the September 97 issue of Microsoft Systems Journal (MSJ). Its title is "Extend Developer Studio 97 with Your Own Macros, Add-ins and Wizards" and the author is Steve Zimmermann. The article covers macros and add-ins very well, but admittedly discards the theme of wizards. If you want to read about Developer Studio custom AppWizards, then we can point you to a couple of other pieces. One appeared in the March 97 issue of MSJ and is "Write Your Own C++ AppWizards" by Walter Oney. In the same month, Windows Tech Journal published a similar piece—written by me—called "A New Assistant".
The latter two articles, however, cover the Developer Studio custom AppWizards, but not how to write stand-alone wizards, like the one described in this chapter. As explained above the internal details of a wizard are a subject far beyond the scope of the book. Since wizards are nothing more than a Windows 95 common control, then you can check out "Programming the Windows 95 User Interface" by Nancy Winnick Cluts, which is published by Microsoft Press.