[WARNING: Lots of spoilers ahead!]
In this conclusion to McNamee's Navigator series, the evil Harsh have decided to eliminate Owen and the Resisters once and for all--along with their entire world. As the Harsh amass their army, Owen and the Resisters must struggle to defend the still-damaged Workhouse. The book cycles between many points of view: Among others, it follows Owen, who sets off through time with Silkey to unravel a mysterious song about a Frost Child that may be the key to defeating the Harsh; Cati and Wesley, who seek to uncover a spy who is sabotaging the defense effort at the Workhouse; and Rosie, who has fled from Harsh-controlled Hadima to warn the Resisters and to support them in their fight.
Can anybody say "retcon?" In addition to problems with plot holes and series continuity (see my other reviews of this series), this novel introduces what at first appears to be a problematic love triangle. Silkey, the tough Raggie girl who first met Owen in Book 1 (and barely exchanged a few words with him) and who was retconned to have a crush on him in Book 2, now suddenly becomes his companion--and blossoming love interest--for much of the book, and readers are left to wonder what will happen when Owen reunites with Cati. But wonder no more! For in the short time Cati spends with Wesley (another Raggie) at the Workhouse, the two also fall in love, and it is revealed--or rather, retconned--that Cati and Wesley are just really good friends. McNamee is free to do with his characters as he wishes--it is his world--but all of the romance happened too quickly and too unrealistically for me; that part of the novel's conclusion felt very contrived.
The climax to the book was interesting, but certainly not thrilling. The Harsh are defeated by Owen's simple action of throwing a book (about the Harash) into the time vortex in Mary White's clock. This might seem more interesting or original, had not the protagonists taken the same clock in the climax of Book 2 and thrown a time-containing "tempod" into it. Where did this clock come from, anyway? To use the clock again at the end of Book 3 wasn't necessarily bad--it kind of reminded me of the Neverending Story in its slightly anticlimactic simplicity--but it just didn't feel very imaginative, considering that it was essentially a repeat of the ending of the book before it. Ironically, this ending is supposed to emphasize the power of imagination, but it didn't actually feel very imaginatively written.
I enjoyed this novel more than The Navigator, but ultimately liked it less than City of Time. As with previous installments in the series, I found myself scratching my head many times throughout my reading of The Frost Child, trying to figure out how I had missed so many key bits of plot information. (I didn't; McNamee just left a lot of plot holes.) I was similarly frustrated with the constant reiteration of Rosie's obvious brainwashing (how many times do I need to hear she has music ringing in her head?), something that wasn't discovered or resolved until right near the climax of the book.
Ultimately, The Frost Child was a good book, though I have read a lot of better fantasy that I would more readily recommend. Readers young and old could enjoy this book; it's probably even appropriate for middle-grade readers, though YA and adult readers will definitely get more out of it. There is more violence in this novel than in previous installments (e.g., Johnston dies with a knife to the throat), but it's nothing too scary or scarring. Try reading it and see what you think!