By Maria V. Snyder.
Poison Study and its sequel, Magic Study, were extremely engrossing despite some annoying typos (missing commas, periods, wrong words). Snyder is apparently one of those authors who asks herself, "What is the worst that can happen to my characters?" and then does it, which can be painful for a reader like myself, but it didn't end too badly.*
Yelena starts as a young woman waiting to be executed. (One of the annoyances I felt is that I don't think her actual age, 20, was mentioned until the very end of the book. She seems older in some ways.) When she's offered the chance to become the Commander's taste tester instead of hanging, she takes it. Unfortunately, one of the Commander's generals, the father of the boy she murdered, would rather see her dead, as would several others.
The real strength of this book is its powerful characters and relationships. While the setting isn't bad, the plot is really character-centered. Yelena is resourceful and intelligent but still tries to do what's right, even when pushed to her limits. What makes it more interesting is that she respects the Commander for establishing order in her country, even though he is a usurper. Valek, the Commander's chief of security, though crafty, is also mostly likable. (He sure made it obvious he was a liar at the very start, didn't he?)
On the other hand, not everyone's actions made sense. The southern magician who tries to kill Yelena early on is a good example. It just doesn't make sense in light of the magician's later actions. (Killing someone tends to be a last resort rather than a first.) There is also intrigue in the castle which is never fully explained: some secret information about Yelena is leaked, but the person she believes responsible appears to be vindicated... or is she?
Overall, the author keeps the tension level** high without making it unbearable, and resolves the conflicts between several of the characters in a reasonable way. (The southern magician is a glaring exception.) However, there is some oblique sex and less oblique rape, so this probably isn't for children. There is also a transgender issue.
This is definitely more character-centered than epic fantasy, although the view opens up a bit more in the second book. For people who like this kind of thing, I think it's great.***
* (Fire Study, the third book in the series, just came out, but I haven't read it yet.)
** (Although it helped lower the tension, at least for me, to have read Sigmund Brouwer's Magnus, a great historical fantasy that doesn't have any magic unexplained by (actual) science. Anybody even heard of this? You will notice a plot similarity that appears in Poison Study's first few chapters if you have read it. And the "great" should be taken with a grain of salt since, although I thought it was exciting, I was significantly younger and less critical when I read it. I should probably reread it sometime and see if I still like it.)
*** (You might argue that there is some "my character is the center of the world" going on here, since Yelena survives this book due to a more-or-less incredible sequence of coincidences and saves, indirectly, many other people in the second book. If you think about it, that means they were also saved as a result of a more-or-less incredible series of coincidences.)