Quick-take: Enjoyable with a few tedious chapters.
Opal Yong-ae is on a quest to save her father and her boyfriend Nik from a deadly arena.
Far, far, too much time is spent on Opal arguing with her father. Now that she is an adult, Opal feels confident enough to take a stand about past grievances. They debate child-rearing decisions, discipline techniques, and other standard father-daughter tensions that have been detailed in various books since time immemorial.
These discussions are exhausting in real life, and it is exhausting to read. I wouldn't mind reading it a bit to show this classic tension. However, the conversion kept going in circles. Yes, it does in real life, but it did in the book too. Many times. I actually blurted out, "Yes, raising a daughter is hard. Yes, the daughter can misinterpret intent. We just went over all this!" This dragged on an entire chapter. Opal even said they are talking in circles.
Once we got that squared away (or deferred to be discussed all over again), it was time for Opal and Nik to have a discussion of their hopes, dreams, and relationships. Boo. I wanted to read about dragons and magic living in an urban environment. Not relationships and daddy issues.
Eventually, the book did get going to epic battles for epic conclusions. I somewhat feel like Rachel Aaron cheated with her own magic system a bit. I don't know much about creative writing, but I do know if you give the hero a useful power, then that hero must begin using that power any time it becomes expedient. Opal is no longer a bad mage in this book, and I feel like she was holding back quite a bit. Also, I felt like Rachel Aaron started making up new convenient magic mechanics to help Opal. Opal would say, "This is crazy! I can't believe I am trying this!" And, of course, it would work.
Score: 3/5. The DFZ was an enjoyable series. The Heartstrikers was better.