The episode was their first arc - "Jet Fuel Formula" - and Googling the quote coughs up the twelfth episode specifically. The book was titled Sex on Planet X.
I caught that myself about 15 years ago. Right about the same time I figured out where "The Ruby Yacht of Omar Khayyam" came from.
26 posted on 09/23/2004 2:45:20 PM PDT by Alex Murphy
(Psalm 73)