Hidden Fires was my introduction to the world of Nuala, and I went into this book with no idea what to expect. I was pleasantly surprised by the depth of the worldbuilding and political structures navigated by several interesting protagonists. The prose was stylish and tight.
Although realism is often a challenge with galaxy spanning SF (hence the distinction between "Hard SF" and "Space Opera") much of the science in Hidden Fires feels grounded and believable, making it closer to the former than the latter. This book feels more like a political thriller to me than anything else. Like many political dust-ups, the impetus for the problems faced by the protagonists were either tragic misunderstandings or failures to correctly read the political situation, which made for interesting twists as well as a believable story.
Even with no knowledge of the prior books I was able to follow the story and look forward to learning more about the world and characters in the other books of the series.