I really felt like A Duty to the Dead was an extremely well-written mystery. The book was full of feeling and heart, the heroine was kind and tender, but also brave and tough (in fact, she reminded me a great deal of Jane Eyre), and the profession that she had was unique and made it plausible for her to find herself in the situations that she found herself in. I was also pleased with the denouement. It wasn't a shocking one, but it was a believable and sadly satisfying one. I didn't have this mystery figured out, which is always a plus.
There were some very emotional passages in this book, and some very important issues, such as PTSD, were taken up here. The way the authors wove the big issues into the story gave it weight and substance beyond what I think is normally found in your average mystery story. This was a mystery story about war, family, duty and honor. But mainly, this was a well told story.