The central character is Liir, a minor but not insignificant figure in Wicked, who may or may not be Elphaba's son. The story follows his attempts to come to terms with the mysteries of his self and past, always at least potentially defined in terms of Elphaba, but in many ways its other absent centre is the appropriately named Nor, whom Liir seeks because she seems to represent a tangible link to his past (and, implicitly, to the traumatic circumstances of his separation from Elphaba in Wicked, and that latter's death). Ranging across the whole of Oz, Son of a Witch achieves the same compelling mosaic effect as did Wicked in its reimagining of Baum's magical land, although I didn't feel it to be perfect in the way that the first book is.
Liir is a strange sort of character; for much of the novel, he comes across as a cipher, his motivations and desires unclear. I'm inclined to give Maguire the benefit of the doubt and believe that the author intended this, for Liir is presented as himself being almost definitionally unsure about who he is and what he wants, but the effect is nonetheless to distance the reader from the novel's central protagonist, resulting in less emotional investment than might otherwise have been the case, and it wasn't until more than halfway through (from the sections when Liir and Candle first repair to the Apple Press Farm) that I felt that I'd been really grabbed by the story and characters. This feeling of distance from the characters is augmented by the way in which figures, many familiar from Wicked - Dorothy, the Scarecrow, the Lady Glinda, Yackle, and others - seem to drift in and out of Liir's story (I found myself wondering how well this novel would have stood alone, had I not read Wicked - and read it several times, at that), often not being particularly deeply or obviously characterised.
Also adding to this feeling are the - at places quite extended - discursive excursions which Maguire dares, usually if not always grounded in Liir's thoughts. One example which sticks in my mind is the passage in which Liir wonders about the relationship between Candle's music and his own memories of the past, throwing at least half of the narrative to that point into question; another is a very nice treatment of memory and recollection which touches upon an issue dear to my own heart:
His other talent, though, was a distillation of memory into something rich and urgent. He guessed, in the hours or years remaining to him, he would remember the effect of Trism clearly, without corruption, as a secret pulse held in a pocket somewhere behind the heart.
The exact look of Trism, though, the scent and heft of him, the feel of him, would probably decay into imprecision, a shadowy form, unseen but imagined. Hardly distinguishable from an extra chimney in a valley formed by pantiled roofs of a mauntery.
In a strange way, these kinds of passages also add to the self-reification of Maguire's novel as a retold (retooled) fairy tale - a fable - with their sense of imparting a distilled wisdom of sorts, though a wisdom expressible only in questions and revealed uncertainties, and never in final answers or simple moralising. At heart, of course, it's a fantasy - but it's a thoughtful, critical, and also very political and moral fantasy (nb distinction between 'moral' and 'moralising'). It didn't touch me as much as did Wicked, and I think that it's much in the shadow of that earlier book (even more so than was necessarily implied by its nature as a sequel), but Son of a Witch is still really rather good.