Since this is a book whose main topic is scriptlets, it should be quite unlikely to find related topics for which you may need further reading. In fact, we're supposed to give you a complete programmer's reference for scriptlet programming.
However, in this section we'd like to point you in the direction of a couple of references that can constitute a quick tutorial on the subject. While this book is going to cover the same topics in more detail, you may need a brief but complete overview of scriptlet programming, too.
If this is the case, then check out the Cutting Edge column in the January 98 issue of MIND, (Microsoft Internet Developer) where you can read a complete presentation of scriptlets. In particular, it also provides a DevStudio 97 wizard for generating simple scriptlets. Another source of quick-but-complete information is "Professional IE4 Programming", written by various authors and published by WROX Press, ISBN 1-861000-70-7. The book includes a chapter dedicated to scriptlets.
Again, if you need to focus on the specific features of the DHTML object model, then what's better than picking up "Instant IE4 DHTML Programmer's Reference" ISBN 1-861000-68-5 by Alex Homer and Chris Ullman, also published by WROX Press?
ActiveX controls and categories are well covered by David Chappell in his "Understanding ActiveX and OLE" from Microsoft Press. ISBN 1-57231-216-5..
Do you want to know more about the customization features of Developer Studio 97? Then, be sure to check out Steve Zimmerman's "Extend Developer Studio 97 with Your Own Add-ins, Macros, and Wizards" in Microsoft Systems Journal (MSJ), September 97.