This is an excellent book, and sits comfortably alongside all previous books in the series. I am thoroughly impressed that the author is maintaining the high standards that he has set himself.
Pleasingly, this book follows a very different structure to those before it. There are 5 key story threads each of which follows a different group of destroyer men and cats as they try to complete the arduous task that they have been set. This approach allows several minor characters from earlier books to get a lot more attention, and not all are successful in their endeavours. The Grik pleasingly get only a small amount of attention in this book, other enemies are given some proper attention instead.
I think my only complaint is one I mentioned in the last book. The speed that technology is progressing is far too fast. I am particularly concerned at the ease in which massive engines for steam ships are constructed and installed. The storyline involving aircraft is also just too much and thus becomes unbelievable.
That said, it is an excellent read, the author is managing the overall plot development very well. There is plenty of scope for another half dozen books in the series over the next few years.