The Mystery Science Theater 3000 Amazing Colossal Episode Guide was produced by MST3K/Best Brains writers and performers Trace Beaulieu, Paul Chaplin, Frank Conniff, Jim Mallon, Kevin Murphy, Michael J. Nelson, and Mary Jo Pehl. Published in 1996 by Bantam. ISBN: 0-553-37783-3.
The Episode Guide contains writeups for every episode from seasons 1-6 and "previews" of the movies to be MSTied in season 7. Each writeup contains a movie synopsis, a description of each of the segments featuring Joel/Mike and the 'bots, and "behind the scenes" reflections from Trace, Mary Jo, Mike, et al. When appropriate, the writeups also include a nifty box detailing various facts about the movie's monster(s), their special powers, weaknesses, etc.
Beyond the sundry episode synopses, there is quite a bit of additional reading material. Each author has contributed an introductory chapter: Mike wrote the "Introduction," Kevin wrote the "Forward About Kurt Vonnegut," Trace wrote the "Introduction to the Preface," Mary Jo wrote the "Preface," Paul wrote the "Acknowledgements," and Jim wrote the "Introduction to the Special Platinum Edition of The MST3K Amazing Colossal Episode Guide." There's also a great section on the history of MST3K, a chapter discussing the then-forthcoming Mystery Science Theater 3000: The Movie, and appendices devoted to Frequently Asked Questions and the meaning behind fifty of MST3K's most obscure references.
Postscript: The Episode Guide was incredibly popular and fans soon clamored for an updated version. Rather than republish the Guide, the MST3K crowd opted to post writeups for seasons 8, 9, and 10 on the show's website: http://www.scifi.com/mst3000/experiments
Update (9 Dec 2002): Servo5678 was nice enough to point out that extended synopses of the Season 7 episodes are available online at http://www.mst3kinfo.com