The Clown Service

The Clown Service is a speculative fiction/spy novel by Guy Adams. The main character, Toby, is a British spy with PTSD who gets transferred to Section 37, a neglected branch of the British intelligence operations dedicated to dealing with the paranormal. In his new job he finds out that there is a lot more to the world than he ever thought possible. Soon Toby has to step forward and save the country from a peril he would have found ludicrous mere days previously.

It is a very Troperrific novel.

Tropes used in The Clown Service include:

Abandoned Warehouse: Visited multiple times.
Addictive Magic: Or more accurately, addictive astral projection. Even when the projection is to a horror dimension.
Alien Geometries: On a pet dog being walked in the other dimension.
And I Must Scream: Krishnin avoids this fate only because Toby changes the timeline by shooting Krishnin back in the sixties.
Astral Projection: Can be done with the help of illegal drugs by the people who have the talent.
Cold-Blooded Torture: Done by Krishnin. with a fork even.
Cold War: The setting of the segments set in the sixties and also the basis for the plot.
Complete Monster: Olag Krishnin. The book even makes it clear that he was evil from childhood.
Creepy Child: Young Krishnin. The evil is visible in his eyes.
Dark World: There is an alternate version of the world that can be accessed by certain people with special powers but who can also take other people with them. It is inhabited by monstrous, distorted versions of people and animals.
Daylight Horror
Demonic Possession: Or possession by whatever the Legion is.
Disability Superpower: Who knew that PTSD could be turned into a weapon against extradimensional horrors?
Fantasy Kitchen Sink: Pixies, leprechauns, yetis, Chinese dragon gods... The list goes on. It is implied that the list goes on very long indeed.
Foregone Conclusion: That Toby survives and England remains just fine, given how Toby is narrating about his past and adding the occasional side remark about future things. This makes the Zombie Apocalypse particularly surprising when it happens.
For the Evulz: Krishnin doesn't care about serving the Soviet Union. He only does what he does because he can.
Functional Magic
Golem: Made with the traditional Jewish lore, with the true name of God and all.
Government Agency of Fiction: Section 37, also known as the Clown Service.
Humanoid Abomination: All the inhabitants in the alternate reality.
I Love the Dead: A mild example. Krishnin, unafraid of the German bombers, dances with a corpse of a girl who had minutes previously died in the bombing raid that had prematurely ended the party.
Intangible Man: Done with astral projection.
Living Statue: A bust of (Herbert?) Kitchener.
Magitech: Genetics and chemistry play a part in creating zombies.
Murderous Mannequin: The story remarks multiple times how the zombies look like mannequins with their glistening, plastic-like surfaces.
Our Zombies Are Different: Type C, like golems but made from dead people.
Perception Filter: Cyril is permanently affected by one. He has to remind his wife every morning about his existence, but his condition makes him an excellent infiltrator.
- A warehouse is hidden with a spell to make people not notice the building even when they're walking straight past it.
Race Against the Clock: Subverted. The number station countdown is nowhere close to zero when Krishnin puts his plan into action.
Ripple-Effect-Proof Memory: Toby still remembers the other timeline. So does the Legion.
Rise from Your Grave: Done by some zombies on page.
Rogue Agent: Krishnin. His Soviet masters would have eliminated him.
Surreal Horror: In the alternate dimension.
The Mentor: August Shining to Toby.
Time Machine: It works as a portal that cannot be fully controlled and can only function for short periods of time and is also very dangerous to use. The inventor wanted to file a patent.
Who Wants to Live Forever?: Krishnin never considered the downsides to being unkillable.
Year Inside, Hour Outside: Time works strangely in the alternate version of the world. Five minutes can be an hour in the normal world, but it varies.
Zombie Apocalypse: Krishnin's plan unleashes this on England.