This was a bedtime read with my 8 yr old which we both greatly enjoyed. The world of the novel is exactly like ours, but with the small detail that Christianity never caught on and the established religion is Norse. This shift was accomplished thoroughly and seemingly effortlessly with little details like the days being called 'Wodensday' and 'Thorsday' etc and people saying things like "oh my gods". The story begins in the British Museum, which (as well as being integral to the story of course) allows Francesca Simon to integrate details comparing the two religious systems without it ever feeling dry or lecturing. My sleepy 8 yr old happily accepted this world and learnt loads about Norse myth without getting bogged down, confused or losing sight of the story. I particularly enjoyed the idea that the Norse religion had reached the point that modern Christianity in Britain has with relatively few actual believers, but being embedded into the culture. The idea of Viking gods being seen as part of some dry, dull institution is somehow especially amusing!
Freya is a great character. A normal modern girl dragged into an adventure with children from the Dark Ages and a berserk, she's really out of her depth and seen as slightly pathetic by her co-adventurers. The narration focuses on her perspective, although it is third-person, allowing us insight into her thoughts and feelings as she undertakes the extremely daunting challenge set her by Woden.
Aspects of myth are used and incorporated extremely well - even to the point where it is clear which parts of the story deviate from the canon of Norse myth. This is where the set-up of a world based on Norse belief that has become fairly stagnant works best, as Freya is able to question the myths she's been brought up with and compare them to the reality that she is now experiencing. As the blurb above indicates, Freya's quest is all about restoring the gods to youth, but her knowledge of mythology tells her that they don't age. Effectively, the established myths have been PR for the gods. This detail ensures that any readers who aren't greatly familiar with Norse tales will clearly know 'real' myth from what has been added for this story. This demonstrates the respect with which the novel treats the myths and, like so many other aspects of this book, is very clever indeed.
Overall, this adventure is a great addition to a child's library. Although the main character is a girl, there is nothing in the story (or the cover) to spoil boys' enjoyment of it. I would heartily recommend this to lovers of fantasy adventure stories and those who enjoy mythic tales.