This is a story from the Once Upon a Time collection of revisionist fairy tales which is significantly simpler and more juvenile than some of the others (I'm thinking in particular of the more sophisticated works by Cameron Dokey). It's very loosely based on The Princess and the Pea, and features a number of princesses competing in a series of "sensitivity tests" to win the hand of Prince Richard -- who is already in love with one particular girl, Violet, who has entered the contest, determined to win even if she has to fake all the test results.
I don't fault the book for being light and fluffy, though I will say it's a little bit annoying as a reader new to the series to have one volume such as The Storyteller's Daughter establish a set of expectations about tone and quality, and then have a book like Violet Eyes have nothing in common with it other than the fact that it's a revisionist fairy tale. I do, however, fault the book for some of its content.
As a writer, my complaint is that this book is filled with deus ex machina type events and solutions to problems. Not just one, but many. You have to go beyond a willing suspension of disbelief to a place of really, really determined indifference to plotting in order to feel satisfied by how events unfold in this story... aside, of course, from the fact that they end Happily Ever After, which you presumably knew they would (and wanted) when you picked up this book.
And as a person, I feel that I should also acknowledge one other concern that I've noticed another reviewer had, as well: she referred to the book promoting bad behaviors -- especially cheating (as in cheating on a test, not infidelity) and self harm. I can see her point, and I will say I was bothered by the pertinent events when they took place in the story.... and upon further reflection, they are bothering me more and more.
The cheating (i.e finding out about the tests in advance and faking the results) initially seems justifiable because the reader shares Violet's and Richard's belief that the tests are stupid and shouldn't determine their fate. But eventually another character comes right out and says that she won't participate in (much less cheat on) the tests because they're stupid -- which makes Violet's reasoning about cheating look especially bad in comparison.
And then comes the most potentially objectionable act -- Violet has realized that there are tests within the tests, meant to discover whether the girls have the strength of character that is required to be a good queen. I'm sure we all agree that a Queen has to put others before herself, sacrifice for her country, and so forth. Okay. But Violet decides that in order to prove to herself that she is willing to sacrifice and suffer, she needs to hold her hand in a candle flame. To put it mildly, I don't think that was a logical conclusion to draw. I suppose in medieval type times when someone might be burned at the stake for heresy or "witchcraft," a willingness to burn for your ideals can actually be tested... but I suspect the kind of sacrifice or suffering Violet would actually have experienced as Richard's queen has nothing to do with the physical pain of burning, and this was a pretty dumb thing for her to do.
So clearly I think it was a pretty weak choice for the writer to make for Violet in the plot... yet I would really like to stop short of believing it's dangerous for younger readers to encounter this story. I can guarantee that 12 year old me would never have read this book and thought, "Oh! Clearly what I must to to test my eternal love for [my secret crush] is hold my hand in a candle flame!" and I really, really hope most other young readers have a comparable level of discernment. But I do understand that there might be some readers who are dealing with their own problematic instincts for self harming behaviors, and this book could become entangled with that in a negative way.
All in all, this seems to add up to a case for giving Violet Eyes a pass. Honestly, I can't think of anyone who would love it, and if you're just looking for a light and fluffy fairy tale, you can find better, easily. But don't write off the whole Once Upon a Time Series! I already reviewed The Storyteller's Daughter, and I'm about to review Belle, both of which are definitely worth a look if you like fairy tale stories.