"Who Killed Jerusalem?" is a cluster of a book. Imagine Columbo tripping on acid, while quoting Plato and Blake, and you still only have a fraction of what's going on in this book. It defies summary.
That being said, if you are a fan of the delightfully bizarre and moderately symbolic and intellectual, then this book is right up your alley. It's clear that George Brown is a fan of abstract philosophical concepts because "Who Killed Jerusalem?" is positively dripping with them.
In the preface, Brown states that a prior knowledge of the mythologies of William Blake is not necessary to enjoy and understand the novel. But after seeing references to Plato's Cave, which I did catch, and then descriptions of an attractive pink cow (yes, there's an attractive pink cow in this book), which I did not, I thought it would be prudent to at least Google the basics of Blake's work in order to understand what was going on in this book. There are long monologues based on philosophical theory that will make your head spin and hurt. But they are followed by a punchline of the vulgarity and worldliness of Brown's own setting of 1970s San Francisco.
In the end, I did enjoy "Who Killed Jerusalem?" if only because it both made me think, laugh, and wonder if the author was ok when he was writing this. I don't expect this book to gain a wide audience, because it is clear that the literary choices will appeal to a very niche audience.