I absolutely loved 'Runemarks'. Although it's been marketed as a Young Adult book, I enjoyed reading it as much as my daughter and her friends did, and view it as a crossover book that any age group with a penchant for fantasy and magic will thoroughly enjoy. I found it engrossing from the first wonderful sentence: "Seven o'clock on a Monday morning, five hundred years after the End of the World, and goblins had been at the cellar again."
An outsider who has to discover and grow into her power, runes, magic, Norse gods, goblins, sharp humour, action and adventure, and an abundance of clever twists all combine to make this a high-voltage read that's hard to put down. I've read reviews that say you would need some knowledge of the Norse gods to understand this book, but I don't agree. Their characters are part of the story and it's not important to know their mythical backgrounds - though you may find you want to explore them, and the runes, further after reading 'Runemarks.' There's a list of characters and a brief description of the individual runes at the beginning of the book, which makes it easy to see who's who - the cast of characters made me laugh, because it swiftly becomes clear, before you even start to read the book, that Loki is Trouble with a capital T.
If you're expecting a novel along the lines of 'Chocolat', 'The Lollipop Shoes', 'Gentlemen and Players', 'Sleep, Pale Sister,' or any of Joanne's adult books, you'll find 'Runemarks' to be very, very different but just as well-written. As an author she has always admirably resisted being typecast, and 'Runemarks' reveals how extraordinarily versatile she is as a writer.