The story opens with a boy & his unicorn (or a unicorn & her boy) walking down an abandoned highway together. They would probably be content to simply explore this post-apocalyptic world together, living mostly off the land and only coming near cities to take what they need from stores that haven't already been looted by everyone else. Unfortunately there are other people in the world, and one of them is a necromancer who wants Ariel's horn. Also, boys to grow up, and unicorns aren't necessarily compatible with growing up. It is a great coming of age story with good characters and marvelous fight scenes, and I especially enjoyed the author's commentary at the end.
So, mostly I really enjoyed the story, but I had some major problems with the world. The idea of "The Change" where technology suddenly stops working, pollution vanishes, and magical creatures suddenly appear, is fabulous, but the execution isn't perfect. How can watches and compound bows keep working if bicycles don't? What Boyett really wanted to do was to remove guns and modern transportation from the world - which is great - but there are probably better ways to do it. Sky's suggestion was to make combustion suddenly stop working, so engines and guns don't work but other things still do. I'm sure someone else could poke holes through that too. Mostly this didn't bother me though. My big problem was the social changes following the Change. Where did all the people go? Pete & Ariel are wandering through a very sparsely populated landscape, and yet folks didn't all starve to death because there are still canned goods on grocery store shelves. I think they're mostly assumed to have died as a result of violence, but the speed at which society just falls apart just doesn't feel right to me. It doesn't mesh with the fact that so many stores in large cities haven't been completely looted and destroyed.
Anyway, these are the sorts of things that you'd expect to see cropping up in a first novel, and the story is good enough, the action especially, that it is still eminently readable.