The most benign and level-headed is the Narrator, who tells the story for our benefit, and for John's. But John is also plagued by the Academic, who comments on the historical accuracy of John's delusions; the Bastard, who ceaselessly goads and belittles him; the Tempter, who gives him false hope and lures him into situations he can't handle; and the Jester, who just makes light of the whole thing.
John grew up in care and, after a period in which he did his best to fit in with the normal world by going to university and getting married, he had a breakdown. Although he does sometimes set out on missions to find his long-lost brother, he's mainly confined to a homeless shelter in Leith in Edinburgh.
But through his obsession with the paintings of Bruegel he's created an alternative life for himself where he's in the Netherlands in the 16th century during a brutal invasion by the Spanish, in which analogues of himself (Johannes) and his buddies at the shelter (Cornelius and Balthasar) are making their way through the country looking for Johannes's son, kidnapped by the Spaniards to work for them. It's a gruelling quest, fraught with the danger of imminent capture.
As the novel progresses, John's surroundings slip from Leith into old Holland more frequently and with less warning: being picked up by a couple of policemen can switch in the blink of an eye to an interrogation by the Inquisition. As a result of being unmoored in time and harangued by a multitude of inner voices, we find it almost as hard to get our bearings as John does.
Stuart Campbell, who has worked for a mental health charity, has clearly striven for a believable account of living with such a condition without compromising either the authenticity of John's experience or the demands of the narrative. The central thread of the story always holds firm.
And, for all that John can seem like a puppet jerked around by the competing demands of his inner voices, we never lose sight of his humanity, or his need for dignity and self-determination.