Symbolism, Imagery, Allegory
Pop quiz: what does a 14th Century Italian dude who wrote really long poems got to do with a prison sentence in 1991?
A lot, according to Shaka.
He describes his life in prison like this at one point:
Like Dante journeying through the inferno, my life would forever be changed by the things I would witness and take part in— the violence of oppressed against oppressor, predator against prey, and the insane against the criminally insane. (2.28)
This sounds pretty grim, and it is. Dante's Inferno is basically a tour of hell. Dante sees all sorts of horrors, and Shaka is telling us that his life in the prison system was similar.
But what's not quite as obvious is that there are seeds of hope in this metaphor, too. Dante learns a lot from his tour of hell, and he finds something he's been looking for, metaphorically speaking. And then he gets a tour of Purgatory (better than hell), and Paradise (which is, well, paradisiacal). Shaka's use of this image gives us hope that he too is going to find his way and journey to better things eventually.
And that's exactly what he does in the book.