Eliot - I disagree with your proposition that people can't discuss books unless they enjoy the same books, or approach the subject in a sterile, criteria- or issue-based scholarly manner.
People on these 50-Book threads have very different backgrounds and tastes in books, and yet we have managed to have many lively discussions.
It's just like how I can talk about why I love Bach's music with someone who does not know any music theory and listens only to hard rock and blues. I can tell her about the inevitable sense of order in Bach's music even if she has never heard of Tonic, Dominant, or Cadence - how every note feels exactly where it should be and how it progresses through beauty and agony to bring various melodic threads together and arrive at such satisfying conclusions. I can talk about how much pleasure I get from playing 4 or 5 different melodies with only 2 hands to someone who has never heard of a Fugue.
Even if she has never heard of the word Counterpoint, I can tell her that all instruments have their own, equally important melodies in Bach's orchestral works, and that it's wonderfully stimulating to try to follow 2-3 of them at the same time. I would talk about how Deep Purple and Led Zeppelin also do this - quite often, the lead singer's melody is no more prominent than that of the guitar or the bass.
To someone who has never heard of the term Deceptive Cadence, I would talk about the pleasurable agony of delaying an anticipated climax 
What I would not say is that I play three instruments, continue studies in one of them at a Conservatoire, sing Soprano at said Conservatoire, and could not possibly have a conversation on music appreciation with anyone who doesn't have the same tastes, lexicon and frame of reference as me.
Re chick-lit - My earlier comment was not a judgement on relative "cultural value" or worth of one genre above any the but what I personally like and dislike, which followed from you assuming that I'm a Dan Brown/Dean Koontz girl.
"If I did read chick-lit and I read your scathing comments about it, and were a less confident person I would be hesitant to contribute to this thread, because who wants to feel put down for what they read? "
We have been talking openly about books on these threads for many (8?) years and I would think that their atmosphere of candour and bonhomie is well-established. Remus's taste in fiction is the polar opposite of mine, and we have had some great debates over the years. It is OK to say I can't stand a genre, don't understand why people would want to read it, and it's OK for others who do to talk about how they enjoy it.
You should try it
As I said before, I would be interested to read your thoughts on how and why you feel The Master and Margarita is a great novel.