The same characters appear for a second time and they don't meet my "do I care about them" - no I don't if there is a third book I won't buy it. If you were expecting discworld humour you won't find it.
The concepts in the book are interesting but the story is a little contrived and the humour an little stained. I enjoyed it but not on my top recommended list. Be OK to read on holiday to keep you occupied.