From the Recesses of the Dark - R. L. Parker - Bog

Imagine a perfect London; a place with no lawbreakers, no criminals, and no dangers to a peaceful society.
A perfect city that keeps only the most perfect of citizens and throws the rest away behind an unscalable wall into a wasteland known only as Exile. Lewis, an ordinary university student, somehow finds himself cast away with the other dregs of society into this anarchistic land.
Along with the help of a convicted murderer and an unlikely friendship with a possessive sociopath, he soon loses his sense of morality and becomes lost in a dark and villainous version of himself whilst struggling to survive in a land where he must learn to either kill or die.