Publication date: March, 1999
Price: 24.95 US
WWW book information: http://www.oreilly.com/catalog/tclnut/desc.html
It, along with BOOK Tcl/Tk Pocket Reference, are currently the only books at O'Reilly's with Tcl in the title.
However, O'Reilly's does publish the wonderful BOOK Exploring Expect which of course deals extensively with Tcl, as well as the Expect extension.
George Howlett writes, "It's a great reference book. How great? Not only did the authors laboriously go through the BLT manual pages, but compared the source code too. You're right, there's no manual entry [for blt::winop, for example], but they documented it from the sources." (!)