Superficially, at least, Isaac Asimov's Caliban is like many of the Asimov robot novels: a human investigator working with a robot partner to solve a crime against a political background. The way the story is contructed is somewhat similar, as is the restrained use of language and the "feel". But I found this book far superior to any of Asimov's novels.
A crime is committed at Leving Laboratories on the planet of Inferno. The planet's best roboticist has been assaulted, and unbelievably, the attacker seems to have been - a robot. The Sheriff of Hades, Alvar Kresh, is called in to investigate with his robot assistant, Donald. Meanwhile, the presence of Settlers on the planet, called in to assist with Inferno's failing terraforming, complicates matters . . . and the robot Caliban is awake and on the loose, with only a limited understanding of what is around him.
Allen just writes so well, and so much better than Asimov ever did. His characters, both human and robot, leap out at you as real. Alvar Kresh and Fredda Leving, the roboticist, have genuine depth and engage our sympathies. The setting of Inferno is really brought to life, both its geography and people, and we are thus given something that Asimov never gave us: a solid picture of Spacer society. In Caliban, we have the naive observer, who both drives the action and provides a useful commentary on what he sees around him. That commentary links in to the central issues of the novel: why are things the way they are between humans and robots? Is the status quo harmful to both? Fredda's responses to these questions, the actions they lead her into, and what results from them, are really at the heart of this story.
I always really enjoyed Asimov's classic robot novels, but reading Allen's has shown me how limited they are. With his superior characterisation and writing abilities, and the way he takes fresh ideas about robots to their logical conclusion, Allen gives us a more enjoyable and thought-provoking read than Asimov ever did.