I really enjoyed this one. Katherine Roberts has created a world that it's a great pleasure to get lost in. Familiar elements of the Arthur stories are woven seamlessly with the new inventions and children will delight in Rhianna's adventures. It's a treat to see a female protagonist in this kind of novel and, as you can see from the cover, this is not a 'girly' book. I would happily give it to a boy or girl to enjoy.
Rhianna is a fabulous character. At the opening of the book, she doesn't know who she is - she's simply the only human in Avalon, allowing for some 'odd one out' feelings to be explored. As a girl, she faces difficulties in persuading others that she can play an active role in protecting her heritage. She's feisty and determined, in keeping with her unruly red hair, and this can lead her into rashness but she also - sometimes - shows signs of wisdom and cunning in dealing with her enemies.
Her best friend, Prince Elphin of Avalon, accompanies her on her journey into the mortal realm. He is calm and gentle and, as a fairy prince, has magical abilities. He makes a good contrast to Rhianna and allows her a young friend and ally in the uncertain world of mortals, in which she mostly has to deal with adults who (of course) assume they know best.
No review of this book is complete without a mention of the fairy horses ridden by Elphin and Rhianna. These are a brilliant addition, increasing the magic and enchantment in the story, as well as providing the Avalonian pair with more allies. Child readers will love them and dream of their own magical friends, I'm sure.
Overall, this is a tightly-written, classic quest tale with engaging characters and a well thought out premise. There are going to be four in this series, and I will definitely be looking out for the others as they are released.