It is worth reading for those who like novels of scenes and crowds more than of a single hero: The Slum has 23 numbered chapters, without titles, and alternates João Romão's rise with the life of dozens of residents of the tenement, in a narrative that moves along.
What the book gives the reader is a clear plot (a shopkeeper gets rich at others' expense and raises a tenement) and scenes that stay with you: the morning the tenement wakes, the Sunday pagode where the chorado silences the fado, the razor slash and the battle with the police, the quarrel between Piedade and Rita, the fire and the ending with the enslaved woman and the diploma. The characters are fixed in a single trait. Firmo "had no muscles, he had nerves". João Romão has "a desperation to accumulate". Miranda appears at the window with a carving knife, like a sword.
What may get in the way is the naturalist mode of narration: images of animals, mud and plants, and an explanation of actions through environment and instinct that today sounds dated. There are also many people on stage, harsh scenes of violence, illness and downfall, and the language is that of a novel from 1890. Slavery, which is the engine of the ending, appears without filter.
Nothing needs to be known beforehand. The 1890 text is in the public domain, and chapter I already introduces João Romão, Bertoleza and the tenement. Whoever enjoys it can move on to another novel of Rio from the same generation, Quincas Borba, by Machado de Assis, published in book form in 1891, in which the protagonist also settles in Botafogo.