While Phillip and his adopted cousin, Linda, are rowing their boat across the lake where they are vacationing for the summer, they see something impossible. A castle is sunk in the water that no one else can see, and which vanishes when they dive to investigate. When they return during the night to investigate further, their boat is seized by unknown forces and propelled up a river into another world.
There the two children meet Herne, a woodsman who tells them the story of the battle between the good king Kyril Tessarion, and the evil witch, Morgan. An unseen power separates them from Herne, and the children find themselves in the clutches of the witch Ygerna, daughter of Morgan, who claims Linda is really from this world, the last daughter of the witch Morgan.
Ygerna sends the children on a dangerous quest for The Marrow of the World, which is deep within the dwarfs' mountain stronghold. Great danger and personal growth are in store for the two cousins as they go after the marrow and try to return home. Much better than Nichols other adventure novel, A Walk out of the World, but still a little lacking in resonance. ( )

I thought The Marrow of the World had a lot of promise in the beginning, but there was no character development of anyone but the two protagonists, and even that was bad. Also, certain of the adventures seemed to have no point. I like well-written children's fantasy, but this just fizzled after the opening chapters. I was fascinated by how empty the fantasy world that the children visited seemed, as if most of the population had died out, but I think this may have been due to authorial laziness rather than due to any actual world-building.

I only picked this book up because I thought it was one that I had read years ago and had been haunting me ever since. Obviously that was another book, I think with the same illustrator. ( )