The novel Jack Maggs by Peter Carey is based on Great Expectations by Charles Dickens. Charles Dickens himself lived most of his life in London, and, unlike many authors of the period, had experienced a wide range of economic circumstances and thus knew the varied neighborhoods and peoples of London intimately. Peter Carey, however, is a twentieth- (and twenty-first–) century Australian novelist. Although he lived briefly in London, it was not his permanent home, and he did not live there during the nineteenth century.
In so far as Carey replicates information found in Dickens, he reproduces the atmosphere of Victorian London, but the knowledge is secondhand at best. Moreover, Carey is not writing this as a detailed historical reconstruction of life in Victorian London, but as a novelist using Dickens to think through the role of Australia in the Anglophone literary canon. While his description of the characters in the novel is insightful, he is not aiming at historical fidelity. Thus he does not really provide an historically accurate impression of Victorian London. For that, it would be best to read Dickens instead.