This book was based on a short story written by Terry Pratchett prior to writing The Colour of Magic which was then picked up again and made into this book and The Long War. We felt that this wasn't a particularly good example of what either of the individual writers could produce, in fact it was a bit of a let down.
We felt that although it was a large book there wasn't actually much of a story within the pages, it could easily have stayed as a short story, or maybe a series of short stories. It felt as though the writers were a little bit lost while writing the book, they stuffed in new elements throughout with little or no explanation. It almost felt that this was their original brainstorming session rather than a finished book. Each of the little stories in the book on their own were interesting but they weren't expanded enough to fully capture us as readers. Although having said that we did enjoy the way that some of the creatures found on the other earths were used to explain fairy tale characters, but again we wanted more information.
We could notice the two different writers voices, even though only a couple of members of the book club had previously read books by Terry Pratchett. There were often jarring elements where Terry Practchett came through with a ridiculous name, or piece of information. These were juxtaposed with the much more dry, hard science elements from Stephen Baxter.
The main issue we all had with the book is the lack of details in the different worlds, and a bit more explanation as to why things were the way they were on the different earths. Things just seemed to be seen and stated with little reason as to why and how they all linked. We understood that we were following a scientific experiment and that the scientists involved didn't have the answers but maybe some discussion would have helped us to understand the different earths a little better. The fact that these were all earths of exactly the same age, just one step sideways with regard to the things that had happened to them caused us a bit of confusion because normally in books of this nature they involve time slips rather than earth slips.
Overall we gave this book 3 out of 10. We found it to be ultimately disappointing.