The cost of non-violence
This story models a basic motif, observable in important writings like Plato's Republic (in the allegory of the cave), and also the Bible. Bob Marley is regarded by his culture as a modern prophet, and his music is regarded as sacred music by his followers and by fellow Rastafarians. His prophetic insight is simply that humans can live at peace by committing themselves to non-violence. For this, he is continually persecuted, and ultimately, he dies.
When Alex publishes his story (like a gospel account of Marley's life), he is brutally beaten and tortured by the gang who (probably) killed Marley (although technically, the official cause of death is foot cancer). In other words, the forces that operate by violence are hostile and aggressive whenever someone reminds the people under their control that peace was an option.
Political terrorism
This novel shows so clearly how easily a society can slide into corruption. This novel shows that when political leaders are willing to do business with gangs, the fabric of the society crumbles. This novel is so full of paranoia and fear, like when Nina tries to convince Bob Marley to escape his fate. But Marley is unshakeable, and he is not afraid of assassination. Even when he is attacked at his own home by a small army of gangsters, he stays in Jamaica. Marley represents the correct response to political terrorism: fearlessness and security in justice.
Justice and truth
This novel is full of deception and lies. The gang turns over its control three separate times in the course of the novel, as in-fighting and back-stabbing takes its course. The politicians are entirely corrupt, and none of the populace believe in the government, because the political parties are obviously enforcing their rule through gang terrorism. Therefore, the central virtue of the novel is truth and justice, which Bob Marley sings about in his music time and time again. For Marley, truth was a matter of universal love, and the willingness to work through brokenness with a sense of humility and patience.
