Once again I can't remember much about this book, but since I believe I got my hands on all of the Cat's Cradle series then I suspect that I must have read it. From a quick glance over some of the other reviews it seems that this was not a particularly popular Doctor Who novel. In fact one person describes is as 'the most blandest book ever to bear the name of Doctor Who' while another says 'this seems to be a book that the author took out of his draw and decided to throw the Doctor and Ace into it so as to make it a Doctor Who book'. Well, with comments like that (and them being near the top of the list of reviews) I feel that I really should not waste too much time commenting on this book.
Having a look over the blurb though, I noticed that it seems to involve fantasy elements. Granted there is probably not much of a problem with that, however I have always considered Doctor Who to be a work of science fiction, which means that everything eventually has an explanation (even if the scientific laws themselves may be fictional). However, a fantasy story generally does not have explanations, things simply happen because that is the way that it happens (no scientific law involved). When dealing with magic most authors do not go into detail as to how magic works (though some set it in a modern setting, such as the Dresden Files, do).
In Doctor Who books that involve magical or fantasy elements there usually is an explanation. The Doctor is a scientist and he simply cannot have unexplained phenomena scaring people, and thus he will begin to investigate the causes of these phenomena, with the story leading to the conclusion where everything is explained. There is also the motives of a mystery novel, in that there is always an explanation at the end, and we, the reader, can leave satisfied in knowing that the mystery has been revealed. I am not trying to use this as the only way to differentiate fantasy from science-fiction (there are no hard and fast rules, and in many cases the science-fiction/fantasy genre is usually one in the same), but it is just something that I have noticed and wanted to spend some time exploring. ( )

http://nwhyte.livejournal.com/1400715.html

The Seventh Doctor and Ace find themselves in Wales dealing with peculiar mythological creatures leaking through from a parallel world, an adventure that self-consciously references both Delta and the Bannermen and Survival. This is one of the least impressive Doctor Who books I have ever read, and certainly the worst New Adventure that I have got to so far. No matter what you may think of Torchwood, it did this plot and setting rather better, several times. I see various fan sites excoriating the limp writing, flabby characterisation and unresolved plot lines of this book; I shall add a complaint about Welsh and Irish names being randomly jumbled together with unicorns and centaurs, because it's all mythical, y'know. ( )