It’s interesting that the first novel in this Torchwood tie-in range precipitated something the actual series would later cover (a relationship of Owen’s in around 2004 factoring into why he joined Torchwood, in “Fragments”), because this novel much more directly does something a later episode (”Adam”) would do, in introducing a new member of the titular team that infiltrated them as if he’d already been there, leading to particular chaos relationship-wise for Gwen. This is handled oddly brazenly, as the novel makes no indication of this character not being part of the regular line-up for around two thirds of the book. Given how new the series (let alone the book range) were at the time, it’s an interesting (and confusing!) choice, but arguably works to good effect.
What doesn’t work to good effect is how off the characterisations are here, particularly Gwen’s, and how seismic a hammer the novel takes to foundations of the show (the Gwen character in general, the Gwen/Rhys relationship, and Jack’s leadership). It’s bizarre, almost as if Russell T Davies or Chris Chibnall didn’t even vet the book, because what it does is so pivotal to the fundamentals of the show. Having Gwen all but leave Rhys is a very strange thing to leave to a tie-in novel, especially at the very beginning of the show.
Some aspects of the book are interesting (the Cardiff rift from “the other side”; how other affected societies deal with it) but it’s oddly plot-heavy even for all the huge character changes it makes, and that plot isn’t engaging or particularly well-told. One cup of coffee and a dose of retcon.