Halfway through Franz Kafka's The Trial, Josef K, by now locked irrevocably into a legal process he can neither resist nor understand, expresses his hope that "the Interrogation Commission might have discovered not that I was innocent but that I was not so guilty as they had assumed". Judge Savage is, among other things, an absorbing meditation on the same slender lines that separate guilt from innocence, chaos from order, and simplicity from complexity. Like Kafka's novel, Judge Savage explores not whether things have happened, but the hunger we have to know why. Unlike Kafka, Parks has created a gripping domestic drama through which to conduct his investigation.

Daniel Savage has recently been promoted to the position of county court judge in an unnamed English town. His elevation could be because of his ability - he has a swift and discerning intelligence - or because his public school and Oxbridge education have groomed him for establishment responsibilities. Or, in a possibility he refuses to rule out, it could be tokenism: Savage is brown-skinned and was introduced into the English middle classes when his Brazilian mother gave him up as a child for adoption. Savage doesn't discount the option that his insecurity may have more to do with his uncertain parentage than his complexion ("Perhaps adoption was far more important than race?"). Whatever their source, Savage's anxieties have made him tireless in his pursuit of women to whom he is not married.

The book opens with a memorable epigram, as Savage muses on the near-death of his marriage following the exposure of one of his affairs: "There is no life without a double life." Keeping his family together has been so traumatic that he decides to forsake his philandering ways and concentrate on his wife, Hilary, an intention he records triumphantly in his diary. But he cannot escape his former self, who reappears throughout the novel, hammering on the freshly locked door to his past and demanding to be let in.

As he contends with his unravelling life, Savage continues his work in court; Parks uses his ongoing cases like a Greek chorus, to comment on the judge's expanding predicament.

Parks, who lives in Verona and is an accomplished essayist and translator, has written a novel of thrilling range and ambition. Although the book's cover portrays a man whose face is stereotypically black and African, the novel inside the dust jacket subtly undermines the explanatory power of generalised types. Daniel Savage is black, but he is also urbane and rich - as unlike his surname as possible. Expectations are further undermined in the courtroom: every person's story, Parks shows, is unique; Martin, Savage's oldest friend, carries with him a dreadful secret that emerges only after his death. As shock is heaped on shock, Savage's partial-sightedness is given metaphorical force by the eyepatch he is forced to wear after he is subjected to a vicious assault. The laws that once seemed to bind his middle-class group, who were so confident in their knowledge of each other, have been undone.

In law, Savage declares, "duress is a very difficult defence", but the novel shows that in life, it can be everything. When one understands the full peculiarity of a situation, it may actually become more difficult to ascribe innocence and guilt. In the worst case, one may be left understanding nothing other than that one doesn't understand.