This book is the 2nd adventure of Jessica Keller and there's a lot to like - at least for me. Many of the positives of the first adventure are back in the second and it's a lot of fun in many places. I would call this tale for more thoughtful and developed as Jessica in this book suffers some crushing losses. Other things to like is there is quite a bit more background information given about how this war developed and what the adversaries are fighting over.
Perhaps the best way to contrast the two books is that the first book reminded me a lot of movies like Star Wars and Raiders of the Lost Ark #1 - rollicking good fun and the good guys end up kicking butt and taking names. You can watch (or read books like these movies) time and time again and they're just good fun. A nice couple of hours of distraction and high adventure that are just fun, even though you know exactly what's coming.
Book #2 here is far more like The Empire Strikes Back in which the good guys take a significant loss and don't really come out of the adventure with their hides (physically or mentally) intact. I wouldn't call this book a dark tale, but it's certainly not like the more lighthearted first book. Now - all that said, this book is a good read and you do indeed suffer right alongside Jessica. The writing is good and I've liked these two books as a story and am look forwarded to the next book.