Asklemmy

Der Prozess (1915) by Franz Kafka, it still is relevant today.

The Wind-Up Bird Chronicle by Haruki Murakami just a magnificent read, you probably couldn’t go wrong with any of his works.

A long way gone by Ishmael Beah was pretty dark. Story of a boy soldier from Sierra Leone explaining how you get forced into it and the terrible things they did.

Sadly, Porn

I don't know how to describe it, expect to be confused and offended and gaslit.

The Fan Man

The multiorgasmic man.

Definitely House of Leaves. A story inside of a story, inside of a story, with all narrators being just a bit crazy. Text of different fonts, going all over the place and even upside down based on the story. Just make sure to get the physical copy.

Not a book, but a webcomic: https://elan.school/

Be careful what you wish for OP, this is THE WILDEST shit you will ever read (at least top 5, guaranteed) and the worst/best part is that it's all true.

Also, its VERY addictive so clear your schedule.

You've been warned.

You've ALL been warned.

I went into Do Androids Dream of Electric Sheep? blind. Hadn't seen the movie, hadn't read any other Dick, hadn't even had it hyped to me by a friend. What a series of mindfucks.

Fear and Loathing in Las Vegas is an obvious but nonetheless relevant answer. What a ride.

Also Infinite Jest.

I'd say the first book of The Chronicles of Thomas covenant the unbeliever was a wild trip.

In the story, Thomas covenant has leprosy. Due to the leprosy he is numb from the neck down even though he can still walk. He has no sensation when he touches anything and he cannot engage in his chosen profession which is writing. In a fit of pique he rescues a girl that almost gets hit by a car and gets isekaied.

This was written in the late '70s so it was not a common trope at the time.

He arrives in a world of magic on top of a mountain covered in Giant steps, he crawls his way down the mountain and encounters a girl who uses the magic of the land to heal him of his leprosy.

Believing this is all a dream and trying to prove to himself that this is not real, he rapes the girl.

The girls seems very distraught but pulls herself together and guides him into town and that is when he discovers that the white gold wedding ring on his finger is the source of wild magic.

There is a great evil on the land that plans to destroy everything and he is the chosen person, the only person who can stop it.

He has to fight against his disbelief of the world while reconciling his abhorrent actions with his own internal sense of morality in order to have a chance to go home again.

This book spawned a 10 book series covering hundreds of years of history in the land with Thomas Covenant's battle with the forces of evil and the lives of the people of the land resting in his leprosy numbed hands.

It's an amazing work but it is a rough read.

The Road. Still think about it a lot.

Strange new world by Heinlein.
Martian Jesus comes back to earth and is like, wtf guys?

The Book of Rack the Healer by Zach Hughes was pretty wild.

It's 'New wave' sci-fi from the 1970's, and revolves around these mutated humans in a deeply poisonous and radioactive world where it's forbidden to dig into the earth.

The humans have evolved a carapice and internal air sacks that they fill to hold their breath before leaving their safe organic dome homes that change color depending on their mood. Some of the domes have women in them that don't seem capable of complex thought, and live purely through sensory input, are telepathic, and are basically constantly edging themselves all day.

It's a drug fueled fever dream, for sure.

Naked Lunch. It's a dark strange read but it suck with me.

I’m not sure if it’s the wildest but the first that comes to mind is “John Dies at the End”

The one that included the most wildlife might be hard to know exactly, but 'The Lost World' by Arthur Conan Doyle might be a contender.

One of my favourite books, and one that gave me lots to think about was His Dark Materials by Phillip Pullman.

The most 'different' setting for a book that I've read might be The Planiverse by AKA Dewdney, which takes place in a 2d world with thought out and realistic physics and societies.

NOFX: The Hepatitis Bathtub. Wildest because it’s an autobiography, and they spill it all.
Edit: find the audiobook if you can

In elementary school I read this book called "Flawed Dogs" and it was unforgettably wild. It's about a dog who escapes some kinda confinement by jumping over a barbed wire fence and loses his back legs in the process, and then joins a dog gang and does dog gang activities. Also one of the dog gang members was a cat in disguise.
Honestly I should see if I can find a copy of it and reread it. It was pretty wild.

edit: I looked it up and maybe I have a lot of the details wrong but it's still pretty wild

Dhalgren by Samuel Delany

(Close race with House of Leaves, but ultimately House of Leaves was telling a specific story, whereas Dhalgren is a semi-incoherent drug trip. Loved both books, though.)

I don't know about wild, but UNSONG has been a very weird trip. It's like science fiction, except instead of science its Jewish kabbalah. There's angels, demons, alt history American politics, religious references that are truly esoteric, and puns... lots and lots of puns.

Kitchen Confidential.

Depends in what way you mean 'wild.' Crazy even psychedelic, but nonetheless benign? Or are we including disturbing?