The novel has a tendency to sprawl, with too many characters and too much to say. Yet Byatt takes tender care with the reader. She is a careful guide, and though this entry is at times a lot to process, it’s a worthwhile journey.

While Byatt’s engagement with the period’s over­lapping circles of artists and reformers is serious and deep, so much is stuffed into “The Children’s Book” that it can be hard to see the magic forest for all the historical lumber — let alone the light at the end of the narrative tunnel. The action is sometimes cut off at awkward moments by ponderous newsreel-style voice-over or potted lectures in cultural history. Startling revelations are dropped in almost nonchalantly and not picked up again until dozens or even hundreds of pages later. Byatt’s coda on the Great War, dispatched in scarcely more pages than the Exposition Universelle, is devastating in its restraint. But too often readers may feel as if they’re marooned in the back galleries of a museum with a frighteningly energetic docent.

Byatt’s characters are themselves her dutiful puppets, always squeezed and shaped for available meaning. The Children’s Book has a cumulative energy and intelligence, and the unavoidable scythe of the Great War brings its own power to the narration, but nowhere in its hundreds of pages is there a single moment like the Countess Rostova’s free and mysterious irritation.

As in her Booker Prize–winning novel, Possession, here Byatt has constructed a complete and complex world, a gorgeous bolt of fiction, in this case pinned to British events and characters from the 1870s to the end of the Great War...the magic is in the way Byatt suffuses her novel with details, from the shimmery sets of a marionette show to clay mixtures and pottery glazes.

It begins with the discovery of a boy hiding in a museum.

The time is 1895, the boy is Philip Warren, and the museum is the precursor to the Victoria & Albert: the South Kensington Museum. And, oh, yes –there’s a remarkable piece of art that the boy is besotted with — the Gloucester Candlestick. However, while this may make many children’s book mavens think immediately of E. L. Konigsburg’s classical story for children, let me say straight out — A. S. Byatt’s The Children’s Book is a book for grown-ups. It is emphatically not a children’s book although it is about children, about books, about art, about the writing of children’s books, about the telling of children’s stories, about the clash between life and art, and about a whole lot more. A saga of a book teeming with complex characters, fascinating settings, intellectual provocations, and erudite prose, it gets under your skin as you get deeper and deeper into it and won’t let you go even after you reach the last page....