He speculates convincingly about likely literary sources, and time and time again opens new windows on familiar texts. There are no ritual genuflexions at the usual shrines.
Of Hans Christian Andersen - who "broadcast a sentimental religiosity across the surface of his work" - he says that "every one of his tales is coloured by the witch's blood of self-pity". "Two English gentlemen on their knees, worshipping a goat," is his comment on Kenneth Grahame and the "Piper at the Gates of Dawn" chapter in The Wind in the Willows. J R R Tolkien's The Lord of the Rings derives its "fake exultations of the battlefield" largely from Wagner, and he quotes a plummy passage with the remark: "Very seldom does one encounter emotion this fraudulent and writing this bad in any genre."
But he reserves his greatest scorn for the Narnia Chronicles. Though not all may share his dislike of C S Lewis, even Narnia admirers will be hard put to it to defend this work against the Goldthwaite case for the prosecution.
He approaches the whole genre of make-believe as a Christian moralist, believing that its true genre is "to baptise the imagination". The texts he most values for this purpose are unexpected and include nursery rhymes, Perrault, Uncle Remus, about which he writes with passionate eloquence, Pinocchio, which he especially venerates, Beatrix Potter (with reservations about her lapses into whimsy), Dr Seuss.
There is also Little Black Sambo, in which the story of Little Red Riding Hood is turned on its head with the villain being gobbled up, for "if ever there is a more perfectly composed, more perfectly expressed tale in the English language I do not know of it . . . It is a celebration of nothing more nor less than the happy fact of being a child."
Goldthwaite admits that the history behind the "Sambo" sobriquet is ugly,but refuses to be cowed by current political correctness into denying the tale's literary excellence.
From all this it will be seen that he certainly does not wish for religious indoctrination; indeed he is dismissive of Charles Kingsley's and C S Lewis's attempts to incorporate this into their fantasy. George MacDonald succeeds because he leaves all interpretation to the reader. But though the sermons in The Water Babies are prolix and infuriating, Kingsley does sometimes check his impulse to hector and lecture, and leave his point to be inferred.
A notable instance is with the character of the Irish Woman whom Goldthwaite sees as Lady Wisdom, the same "universal teacher and friend of our need" that we find in MacDonald's North Wind, Carlo Collodi's Blue Fairy, Perrault's fairy godmothers, and 2,000 years before that, the speaking voice in the book of Proverbs. He also draws our attention to some excellent nonsense in Kingsley that in our exasperation we often overlook.
But the Rev Charles Dodgson apparently did not. Goldthwaite suggests that much of Wonderland is a running argument with Kingsley about how one should tell a children's story. He sets out parallel quotations which are indeed remarkably similar, and postulates that Dodgson, always envious of Kingsley, was infuriated that the latter got in first with The Water Babies while he was still expanding the tale he had told to the Liddell children into the book that became Alice's Adventures in Wonderland.
And, abandoning all sense of what is relevant, Goldthwaite lengthily develops roman a clef theories. The author of Alice is admittedly a perplexing character. How could such a prim pedant write anything so anarchic and violent? Why did he reduce Wonderland 25 years later to fatuous sentimental vapourings in The Nursery Alice? And there is the added bonus of the concealed clues that Dodgson, an addict of cryptography,is deemed to have left in his writing.
But trying to reconstruct his hidden thoughts from these clues is a dangerous business, as notorious as "who wrote Shakespeare?" for inducing obsession, and it leads the observer to question the balance of those who get caught up in it.
Certainly these two long chapters upset the balance of a book which in other respects is sensible and wise, and also stimulating and delightfully controversial.
Gillian Avery's latest book is Behold the Child: American Children and Their Books 1621-1922 (Random House Pounds 25).