"A Private Cosmos" by Philip Jose Farmer (1968)

"'Now the scientists had originally constructed the Beller so that it was purely automatic.  It had no mind of its own; it was a device only.  When placed on a man's head, it detected a man's skin potential and automatically extruded two extremely thin but rigid needles.  These bored through the skull and into the brain.'"

A Private Cosmos is the third book in Farmer's World of Tiers series.  The first book, The Maker of Universes, and the second book, The Gates of Creation, have also been reviewed here. 

In a A Private Cosmos, Wolff's adventurer friend Kickaha takes center stage as a malignant form of artificial intelligence threatens the tier-shaped world that Wolff created.  In his battle Kickaha is joined by Anana, Wolff's sister, and also by the half-insane Podarge, the "harpy" introduced in The Maker of Universes.

As science fiction novels go, it's fairly arbitrary and nonsensical.  As an adventure story, it's readable but not involving.  Unlike the two previous novels in the series, there seems to be little internal logic to this one, and the author seems to be making everything up as he goes along.  An obstacle is presented, the characters overcome it, but the manner in which they overcome the obstacle rarely arises from the events which preceded it, or from some larger set of principles that one could deduce from commonalities present in both our world and the World of Tiers.

In the end, the kind of internal logic which A Private Cosmos lacks is what separates an indifferent novel from a good one.  It's like a chess game played between the author and the reader, or a chess game played between the author and himself.  The rules of engagement ought to be obvious, and they should be made clear from the beginning.  A good author will then use these rules to create surprise, or suspense, or a sense of tension in the plot, or even turn these rules on their head by the end of the story.  But the rules will remain rules, and not just a set of conditions that the author adds to as he (or she) goes along.  This is the biggest problem in A Private Cosmos: the rules of the game - if there are any - are never explained.

And then there are the analogies present in the book.  Throughout the narrative, Farmer (through Kickaha) compares the World of Tiers to Earth, and this draws the reader out of the narrative flow.  Even worse, it makes the World of Tiers seem far less alien, and far more artificial.  The world presented in the book could have been presented in far more general language - sans earthy analogies - and it would have come across much stronger.

But oh well.  Again, taken as an adventure story it's not terrible.  It's just not very good.  I'm hoping the next book in the series, Behind the Walls of Terra, improves upon its predecessor.