Authors: Peter van Roy and Seif Haridi
Publisher: MIT Press
Publication date: 2004
While there is no direct connection to Tcl, I'd recommend this book as a good general computer science textbook. In particular, the discussions of how to combine programming paradigms in a single language (something Tcl excels at) and techniques for managing concurrency are well worth a read (although event-driven programming is somewhat neglected). Makes a good modern companion to SICP.