a very useful reference book
This book is another of the excellent 'In a Nutshell' series and follows the same style. It is intended to be a reference book that you 'dip into' rather than one you read from cover to cover.
It briefly describes every command and option in the core Tcl/Tk distribution as well as the most popular extensions to the language. There are short code snippets giving examples of usage of some of the commands and each chapter has a useful introductory section. The format that each command is presented in is generally quite clear but the section on the X Windows extensions, Tk, could do with more explanation. If you are not familiar with the conventions for naming X resources and classes this section will be confusing at first glance.
A good selection of the main extensions to Tcl are described including Expect, incr Tcl, incr Tk, Tix, TclX, BLT, Oratcl, Sybtcl and Tclodbc. There are also two chapters listing the Tcl and Tk C interfaces. These are just lists of the ANSI C prototypes and constants with no explanation of how to use them.
The final chapter on hints and tips gives useful insight into the usual pitfalls that the programmer is likely to get into. Tcl syntax is subtly different to standard C programming so this describes the most common causes of software errors.
Overall, I think this is a very useful reference book for anyone who is writing Tcl/Tk programs.