Absolutely fantastic book! While I do think it would be fabulous for children to read (I don't think it would be appropriate for anyone younger than 10, though), it has more than enough content for adults as well. In fact, I would go so far as to say that I found it more complex and "intellectual" (quotes used because I hate that word) than most grown-up books I've read. And now for a lengthy list of some of the things I especially liked: 
 Lyra feels like a real kid. I've read many kids' books where we are told that the main character is a tomboy and so forth, but then the character never acts like that once the introduction of the story is over with. Lyra, on the other hand, wants to play and be a child throughout the story. She also thinks like a child. While most stories with children will pay some lip service to the idea of childhood, Lyra actually feels genuine. She is also afraid, she doubts herself, she moans and wishes that it could all be happening to someone else instead. She has real character flaws, not just insignificant details tacked on as an afterthought to make the main character seem like less of a super-human. 
 That level of characterization doesn't end with the main character. The other important characters were ambiguous. They had motives of their own that went far beyond "I'm, like, totally evil! MUAHAHA!" Right from the beginning, we think the master of Jordan College is evil because he's trying to poison Lord Asriel only to find out a few pages later that he was only doing so because he was trying to protect Lyra. This continues on throughout the story so that the characters feel real and can never really be pegged as either "good" or "evil." 
 Often, when I read children's novels, there will be bits that make me uncomfortable. A perfect example that comes from a grown-up novel is Lucky You by Carl Hiaason. The main characters are obviously supposed to be Good and they do their whole speech about how murder is wrong, then they leave the main Evil character to die on the island without any guilt whatsoever. Had an Evil character done something like that, it would be thought of as horrible - but because a Good character did it, it's no big deal. These sorts of things make me feel very uncomfortable when found in any novel, but most especially in a kid's book. I hate the thought of exposing my own hypothetical children to that sort of corrupt value system. The Golden Compass had no such moments. There were times when Lyra had to do things that, under ordinary circumstances, I would consider bad, but she always feels guilt about them. They are always acknowledged as being bad, though necessary. At no point did this novel offend my personal morality, and that's saying a whole lot. 
 I also liked all the positive lessons of the story - the triumph of Iorek among the bears tells kids that it's better to be yourself than to weaken yourself trying to be something else; Lyra is afraid, but she masters herself and perseveres anyway, showing kids that it's okay and legitimate to feel afraid, but that they, too, can master their fears. Lyra is also a very active protagonist. She initiates much of the plot in a way that is woefully rare for characters, female ones especially. 
 And finally, Pullman writes with a perfect balance of ideas and action, allowing me to enjoy my reading of the book immensely (I must say, I found myself holding my breath several times while reading) while also giving me plenty to think about once I put the book down. This is an all-over fantastic book that I can't possibly praise enough. I've now ordered the next two books in the series and here's hoping they come soon!