World building may be one of the most interesting aspect of the book. A significant component of the intrigue was to try to figure out what time period it was set in. Several readers at first assumed it was set in the Middle Ages. There's a big school made of stone, they light lamps. But then they mention things like Aerodock, and a center for Atom craft, and they talk about photons, and there is even some vague quantum physics-babble. So it's obviously not Middle Ages. But just when you may begin to think the story is set in the modern times, the world still feels subtly wrong. A lot of kids in it seem to live in Dickensian circumstances, working menial jobs (like Roger, the kitchen boy) or simply running around in the streets, instead of going to school. Apparently in this world there are no laws concerning child labor or mandating universal education.
Adherence to, and departure from, fantasy archetypes
This book played up some fantasy cliches (or shall I say archetypes), while parting with others, and it was interesting to see how the readers reacted to the presence or absence of their favorite archetypes. I vaguely felt that this novel neglected to follow a couple of essential plot requirements for a SF/F book.
-- The stakes against which the character is fighting must be high. Of course, for a young girl to go to the North to rescue children from the hands of an evil organization does sound like pretty tall order, but the stakes are not global: it's just a handful of children under threat, not the world in itself (though there is some talk that shady entities experimenting with Dust are trying to change the world forever, it is very vague). So this does not quite qualify as an archetypal hero's quest story.
-- Unlike in the best stories of this kind, things don't get worse before they get better. Lyra's progress goes rather smoothly, although she has some disconcerting experiences. Still, we don't get a feeling of thickening doom, of dark consequences that would befall the world if she fails.
However, another reader said he liked the way "Golden Compass" wasn't based on the familiar "a hero saves the world" fantasy formula. Other cliches were more palatable to him. For example, most characters Lyra meets are exceptional in some way. It's not just an ordinary bear, it's the king of bears. The witch is not an ordinary witch, she's the queen of the clan. But the reader who did not like formulaic plots had no problem with larger-than-life characters. He said it must be "easier to write about extraordinary characters like kings and leaders of clans. For me it's boring to read about ordinary people leaving ordinary lives, because I live one."
The philosophical premises of the book received praise from CFI
CFI being a club of rationally-minded people, philosophical premises of the book got some attention. A reader noted that while this book has several fantasy tropes -- witches that fly on a piece of pine wood, or talking bears -- it really doesn't have magic. There is no mind-reading or spell casting in it, that's not how this world operates. Readers praised Pullman for making the science-fictional elements in this book part of the natural world. This is where the worldview of this novel differs from "conventional" fantasy, in which the ability to see paranormal, or magical, phenomena is often depends on being "pure of heart"; people who are unable to see / experience magic, are often shown as deniers or simply stupid; in other words, in traditional fantasy and magical realism, ability to experience the supernatural element is subjective. Pullman does the opposite. In his world, fantastic elements exist objectively. Another appealing quality of the novel is that the author plays fair with his world. He sets boundaries and rules in his world, and he doesn't violate them on a whim. That's a problem in certain fantasy, where certain characters get to do what they want and violate what they want, but Pullmann stuck with the rules.
The science-fictional elements are rich with meaning
Science-fictional elements in Pullman's world are rich with meaning. None of them are tacked on arbitrarily or as plot MacGuffins. For example, daemons. It is a testimony to Pullman's great job exploring implications of daemons, that the readers in this group found various daemon-moments the most memorable parts of this book. One reader's favorite scene was where the evildoers try to separate Lyra form her daemon, as this scene demonstrates that a daemon is an intimate aspect of a person, and losing it is a horrible catastrophe. It's not like losing your pet dog. It's like having their arms and legs cut off, or losing part of your personality. Another reader admitted finding that scene traumatic, which attests to its power. The role of daemons was so central to the book, it caused one reader to speculate that the plot of the book will be based on Lyra getting separated from her daemon and trying to get it back. Pullmann is good at exploring many nuances of human/daemon interdependence. For example, children's daemons change shape up until adolescence, when a daemon settles into a shape that best represents the person. As a result, some daemons may acquire a guise undesirable to their human -- for example, a poodle, though the owner might have wanted to have a tiger or a lion instead. And now his daemon will trumpet to the whole world that this person, in his essence, is a poodle.
Daemons are also an expressive instrument to convey the characters' emotions and the deeper undercurrents of their psyches, because a daemon outwardly expresses what goes on inside a character. For example, a reader pointed out, the scene where Mrs. Coulter's monkey daemon attacks Lyra's daemon shows that Mrs. Coulter's true intent towards Lyra is very different from her outward sweetness.
The tropes are rich, but confusing
The presence of daemons doesn't explain as many things as the questions it raises. For example, a reader asked, when a baby is born, where does the daemon come from? We also agreed it was a bit simplistic to to think that a demon represented a soul.
Other fantasy elements in the novel are even more puzzling. For example, what to make of experimental theology? "It's weird that in this world theology involves machinery, and you can do experiments with it! It's very tantalizing, and then he doesn't go anywhere with it," said a reader.
Or the notion that Dust may be a leftover from the original sin. "Huh? What's that about?" a reader asked. "How can particles coming from space have anything to do with a religious concept?"
The aletheiometer was seen by a reader as presenting a paradox; on one hand, it was a cop-out because it told you everything you want to know; on the other hand, it made the reader wonder why didn't Lyra spend all of her time reading it, to find out as much as possible about who the bad and the good guys were?
So, the conclusions. Plusses: a convincing, richly detailed fantasy world that whets the reader's appetite by hinting at deeper links between seemingly unrelated magical elements; likeable characters; the fantastical elements exist objectively in this world. Minuses: some fantasy archetypes in the book are too cliche; some science-fictional elements don't seem to be internally consistent.