There are a surprising number of books on Tcl/Tk, extensions to Tcl/Tk, and Tk as an extension to other languages. Here we mention just a few of the well-known books that will get you started with building Tcl/Tk GUIs, which can then be interfaced to your Prolog applications.
Practical Programming in Tcl and Tk - Brent Welch. Prentice Hall,
1999. 3rd Edition ISBN: 0-13-022028-0 http://www.beedub.com/book/
Tcl and the Tk Toolkit - John Ousterhout, Addison-Wesley, 1994, ISBN 0-201-63337-X
Tcl/Tk Pocket Reference - Paul Raines, 1st Ed., Oct. 1998, ISBN 1-56592-498-3
Tcl/Tk in a Nutshell - Paul Raines & Jeff Tranter, 1st Ed., March 1999, 1-56592-433-9
Also visit the books section of the Ajuba Solutions web site:
<http://dev.scriptics.com/resource/doc/books/>
Another list of Tcl/Tk books can be found at the Tcl Consortium web site:
http://www.tclconsortium.org/resources/books.html