Pandemonium, the first novel from the author of one of my favourite reads of all time, We Are All Completely Fine, is a decent high-concept thriller with an interesting hook that never really lives up to its awesome potential.
Taking place in a world much like our own, but with the critical difference that demonic possession occurs openly and is widely acknowledged (even if whether said demons are evil spirits or something else is hotly debated), Pandemonium is told from the perspective of Del, a young man who was possessed by one such demon when he was young. His story is different from almost everyone else who has ever been possessed, however, in that his demon has never gone away and remains locked inside of him, desperate to escape. Del seeks answers from his former therapist and multiple others, all while getting closer to the truth of what is actually scraping the inside of his mind with increasing power ...
Part thriller, part road-read, part fantasy, Pandemonium has a few relatively dark and frightening scenes, but for a story about demons, this remains a relatively horor-free book. Instead, Gregory piles on the mystery about the etiology of the demons and the part that Del may play in their origins being revealed.
It's a great-set up, and for a first novel, Gregory's prose shines. His ear for dialogue is spot on, and his characters - especially Del - feel fully realised and easy to connect with. Which makes it all the more disappointing that the last third of the novel falls somewhat flat, with the eventual revelation being fairly standard and not able to justify the lengthy journey to get there.
Still, this is a first published novel, and is impressive enough on that basis. It's certainly readable and most readers will likely enjoy the journey if they can keep their overall expectations in check.
3 Unwanted Passengers for Pandemonium.