I liked it but I didn't think it was one of her best. What I love about Diana Wynne Jones' writing is the way she manages to write families and characters who belong to families with such a natural touch. Also, although the families are often dysfunctional in quite a functional and/or believable way. So different from the separatist world of a lot of children's and adult's fiction. In this case whole scope of the story and the size of the world it's taking place in gets in the way a bit.
The other thing I was really interested in was the theme of tourism as a force that can be all-consuming and potentially damaging and exploitative to cultures. Unfortunately, I've grown out of the way it's presented in this book. I bet it would still be a real eye-opener to the kids for whom the book is intended, so I'm not marking it down on that account.