I have finished The Children's Book, and I think it's really good, well worth reading if you like long rambling novels with lots of characters. That type of novel works very well for me on audio. Everyone was right however who warned about the long undigested chunks of research just dumped into the text. I think the inclusion of authorial digressions on contemporary political developments (or whatever) was an OK decision, but I think having made that decision, perhaps in a slightly defiant frame of mind, she should have taken as much care to work and rework these sections as she did for the rest of her book. The dense elaboration of her research mirrors the decoration and embroidery of artefacts throughout the novel, but she should have also adopted the craft values of her artisans, and worked and reworked them instead of leaving them rough and undigested. It's a real flaw, but for me it did not even slightly outweigh the richness of the rest.
Setting that aside, I think the newspaper reviews I have read were unfair and ungenerous to the novel, and made it sound more finger-wagging Daily-Mail-ish, than it really was. The reviews I read (excluding those of online friends of course) implied the novel told the story of a selfish woman whose dedication to her work made her a bad mother, and destroyed her childrens' lives. The worst also implied that the movement several characters make upwards into more affluent classes is a source of misery to themselves and others. Nope to both themes. This would be dull conservative stuff indeed.
Instead the novel takes a many-sided view of the evolution of modern society, the rights of women for example, and the damage that the old systems, and the fight against them, did to individuals. But the most destructive forces are those of violent male privilege, in particular the control and abuse of helpless children.
Perhaps the core theme of the book is what art entails. I was reminded of what Nietzsche said about artists, but when I looked for the right quote I couldn't find it. But all the quotes from Nietzsche I found about art did align with this book, I thought, for example:
Art is dangerous for the artist. When art seizes an individual powerfully, it draws him back to the views of those times when art flowered most vigorously; then its effect is to form by retrogression. The artist comes more and more to revere sudden excitements, believes in gods and demons, imbues nature with a soul, hates science, becomes unchangeable in his moods like the men of antiquity, and desires an overthrow of all conditions that are not favorable to art, and this with the vehemence and unreasonableness of a child.