Alta is the sequel to Joust, which was originally written as a novella and then expanded into a novel. I liked the world and the story, but I was a bit disappointed that the novel version of Joust didn't really add anything to the plot. Some elements of Alta probably make a little more sense having already read Joust, but it stands on its own reasonably well.
Readers familiar with Lackey's solo work will not be surprised to find an engaging protagonist surrounded by interesting, likable supporting characters and challenged by wholly evil villains, a world that seems like a nice place to live (except for the villains), and a plot with plenty of action and excitement. Some of the coincidences require some suspension of disbelief, but nothing that I couldn't handle. No huge surprises, but enough variety along the way that it's worth reading. The biggest problem I had is that a few times, Lackey seems to just be running down the list of supporting characters and mechanically describing how each one is handling the situation; while I assume she means to make the supporting characters stand out as distinct individuals, the effect for me is a mushy amalgam of a bunch of different characters. In trying to show us how every one of the characters in the scene, she ends up not helping us know any of them.
I find myself wondering if the lessons about evil people in power and patriotism as a means of oppression are really meant to comment specifically on our current government, or if it's my own feelings speaking. I certainly saw a lot of parallels between Alta and the United States in 2004.
This book ends with the most immediate problems solved reasonably well, but enough big issues still waiting that I assume we can expect at least one more book.
I think this book is being marketed as a YA book. There's no explicit sex; there is some violence, but no really graphic stuff "on camera", and it's very easy to tell the good guys from the bad. But it doesn't compromise being a good book to be a YA book.
Overall, this is a solid Lackey book, one of her better efforts. Not Great Literature, but a good read. I give it a 9 out of 10.