Hambly writes adults, a rarity in the fantasy genre; in particular,
Dragonsbane is a depiction of middle-aged regret, of people who because of historical circumstances and personal situations will never achieve what they dream of, and somehow Hambly writes it in a way that's not depressing and that appealed to me even as an adolescent unsympathetic to the failure to achieve. Also, the dragons are cool.
Under no conditions read the sequels. In fact, let us agree that the publishing records lie and no sequels exist. We will all be happier that way.