Title: A Cookbook for the Tool Command Language (Tcl) and the Tk Toolkit
Rather than a printed book, this is an online "cookbook" approach to learning Tcl and Tk.
Discussion: The last time I checked, this cookbook had not been updated for quite some time, making it a bit dated for people wanting to learn about the most recent features of Tcl and Tk.
Attempts to contact the authors to ask future update intentions have not been successful. That's really too bad - if the content moved to this wiki, we could keep it up to date ourselves.
See also dkerr