How does Channel 4's Catch-22 differ from the novel?

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The TV adaptation has retained many familiar characters, major moments and overarching storylines which will be familiar to fans of the novel. At times, Heller's dialogue is even replicated word-for-word.

Yet despite all that, the TV version has a very different feeling to the novel. Some of the bitter humour has been lost, and the characters have a habit of speechifying – and there are some important plot differences too.

Below, we've broken down the big similarities and differences between the TV series and the novel:

*If you've not read the book – SPOILERS!*

What's going on in the opening scene?

Although the plot of Catch-22 has been wrestled into chronological order for the TV series, the whole show does actually begin with a flash-forward to a later point in the story.

In the opening moments of episode one, Yossarian (Christopher Abbott) stands naked by his plane on the runway. His face is streaked with blood – and he begins to scream.

What we're seeing on screen is (MILD SPOILER ALERT!) the aftermath of the death of radio-gunner Snowden. This is not exactly a big spoiler because, from the very first pages of the novel, Catch-22 circles back again and again to the "death over Avignon", a moment when Yossarian tries and fails to help a member of his crew who is fatally hit. Snowden lies, whimpering, on the floor of the B-25, his flak suit concealing a "secret" wound. This bloody death completely changes Yossarian's perspective on mortality and is a mental wound he keeps reopening as the full story seeps out. "That was the mission on which Yossarian lost his nerve," Heller writes.

Back on the ground, Yossarian emerges from the plane fully naked and utterly shaken – refusing to wear his gore-soaked uniform ever again.

Is George Clooney's character Scheisskopf true to the novel?

Episode one introduces us to Lieutenant Scheisskopf (George Clooney), a humourless military man who is obsessed with parades. Unfortunately, Yossarian and his naïve patriotic pal Clevinger (Pico Alexander) have ended up in Scheisskopf's training unit, where Scheisskopf is currently berating his men and demanding to know why they can't follow his exacting instructions. Being a "dope" and acting against Yossarian's advice, Clevinger helpfully speaks up with some constructive feedback – and is duly punished. He doesn't ever quite understand why.

This whole section is taken straight from the book, with some chunks of dialogue borrowed almost word-for-word. Also taken from the book is the hilarious and infuriating sequence where Scheisskopf puts Clevinger on trial ("read me back the last line"), as well as the scene between Yossarian and his sex-obsessed lover Mrs Scheisskopf (Marion Scheisskopf) who has an interesting take on God and religion.

The promotion of Major Major Major

One of the most memorable characters in the novel is Major Major Major. Poor Major Major Major! He was meant to be called Caleb, but his dad filled out the birth certificate and secretly gave him the first name Major, middle name Major, surname Major as a hilarious joke.

The ludicrous name has hampered him all the way through his life so far, leaving him isolated and lonely – but in Pianosa things begin "suddenly to improve" and he finds "true happiness" on the basketball court with his newfound friends.

That is, until one fateful day when Colonel Cathcart roars up to the basketball court, promotes him on the spot to squadron commander, and ensures no one will ever be friendly to him again. As Heller writes, "When he turned to his teammates, he encountered a reef of curious, reflective faces all gazing at him woodenly with morose and inscrutable animosity."

The TV series is almost entirely faithful to the scene as it's written in the book, with one crucial difference. In the book, he's actually already Major Major Major Major at this point, having been prematurely promoted during cadet training by "an IBM machine with a sense of humour" – and once a position opens up at the air base, Cathcart moves Major Major up into the senior job to match his existing senior title.

But Channel 4's Catch-22 gets even more humour out of the incident, with Cathcart and his right-hand man Colonel Korn bumping him up from Sergeant Major Major Major to Major Major Major Major because they thought he already was a Major – and it would be an administrative nightmare to undo their mistake. Major Major's misleading name strikes again.

This begins Major Major's retreat from the rest of humanity, as (in both the TV series and the book) he bans anyone from ever entering his office while he's in it.

Hugh Laurie's character Major –– de Coverley

The intimidating, mysterious Major –– de Coverley is an important character in Catch-22, but in the novel he appears only rarely –and speaks even less. Two of his best lines in the book are his no-nonsense command "give me eat," and his follow-up: "Give everybody eat." After being poked in the eye with a flower by an elderly man in Rome, he wears a transparent eyepatch. No one dares ask his first name.

Major –– de Coverley's role has been beefed up a little for the TV series to make room for the considerable acting talents of Hugh Laurie, who has also been allowed to ditch the eyepatch and claim more of his share of the dialogue. So far we've seen him give the seal-of-approval to Milo Minderbinder as the squadron's new mess officer, and we've seen him head off to Rome to secure rental accommodation for his men.

It remains to be seen whether this adaptation of Catch-22 will expand his role even more.

The rise of mess officer Milo Minderbinder

Milo Minderbinder (Daniel David Stewart), 27, is a key character in the novel and he looks set to be a key character in the TV series, too.

This infuriatingly shameless mess-officer is capitalism personified – and is relentless in his pursuit of profit. So far, his storyline has stayed true to the novel as he begins his campaign to take control of the mess hall.

Is episode one's gruesome mid-air death in the novel?

One of the most shocking scenes in episode one happens in mid-air, when the plane next to Yossarian's sustains a direct hit – blasting the pilot out of his seat and onto Yossarian's windscreen. Yossarian stares in horror and the pilot slides away, leaving blood smeared over the glass.

"His face. It was right there," Yossarian tells his friends later. "It was one of those moments when, y'know, it couldn't have been more than half a second less than that but he was - I can see everything. Every hair in his nostril. That crooked tooth. And his eyes - there was no life flashing before them or any of that. Just terror. That's all it was."

This incident feels like it could easily have been in the novel – but it isn't. It's a total invention for the TV series, and it feels like a precursor to the death of Snowden.

Clevinger disappears into a cloud

At the end of episode two, Clevinger's plane disappears into a cloud and is never seen again. This mysterious incident is never explained – and it shakes Yossarian to his core.

As Heller writes in Catch-22, "Eighteen planes had let down through a beaming white cloud off the coast of Elba one afternoon on the way back from the weekly milk run to Parma; seventeen came out. No trace was ever found of the other, not in the air or on the smooth surface of the jade waters below. There was no debris. Helicopters circled the white cloud till sunset. During the night the cloud blew away, and in the morning there was no more Clevinger."

Which characters are missing from the TV show – and which storylines have made the cut?

Many key characters from the novel have survived the leap from page to screen, including the ambitious Colonel Cathcart (who keeps raising the mission count), Colonel Korn (his sidekick), and Doc Daneeka (the self-pitying doctor who explains Catch-22 to Yossarian).

In the hospital tent, we also meet Soldier in White (an entirely-bandaged man who cannot speak) and the Texan (a loud-mouthed and opinionated man who cannot stop speaking), although the original version of this storyline did not involve a physical fight.

But fans of Joseph Heller's novel will spot some major characters who have been cut from the story entirely.

So far, there is no sign of Hungry Joe, the airman who goes mad and has nightmares whenever he completes his missions. There is no sign of his 15-year-old tent-mate Huple, or Huple's cat.

There is also no sign of Chief White Halfoat, the Native American airman who terrorises Captain Flume and plans to die of pneumonia – a shame, as this seems like a wasted opportunity to include some diversity in the cast.

And then there's the Chaplain. In the novel, the Chaplain is an important character – in fact, the opening lines of chapter one are: "It was love at first sight. The first time Yossarian saw the chaplain he fell madly in love with him." Their friendship and mutual respect is central to the story, But while the Chaplain (played by Jay Paulson) does make an appearance in episode two, so far he seems to have been sidelined in the TV adaptation...

The treatment of women in Catch-22

“We made it our mission statement to make the portrayal of women more interesting,” co-writer Luke Davies told Variety. “And not because we think the world has changed, not because we think that outside forces tell us that we need to do that, but because the portrayal of women in the novel is so goddamn awful that it just gave us the heebie-jeebies.” Clooney himself simply described the novel's depiction of women as "terrible".

That's why you'll notice some differences in the way the TV series handles its female characters.

The role of Nurse Duckett (Tessa Ferrer) has been expanded, and she seems to take a shine to Yossarian from the start. This is in stark contrast to the novel, where Yossarian and his friend conspire to sexually assault their stern nurse Duckett in the hospital and reduce her to tears – but THEN, inexplicably, she falls for him and they begin a relationship. It's a storyline in the book that's hard to square.

There have also been some big adjustments when it comes to the prostitutes and the women in Rome.

In episode two, we get an early look at Aarfy's sickening attitude towards women as he meets the maid Michaela (fans of the book will know where that's leading).

Meanwhile, "Nately's whore's kid sister" is re-named Ines and is kept firmly outside the brothel, instead of spending her time running into the bedrooms.

Henry Mudd and the "dead man" in Yossarian's tent

Poor young Henry Mudd! He arrives at the US army base in Pianosa just in time to die, enquiring at the wrong tent and getting himself sent straight up into the air on a fatal bombing mission. He hasn't even unpacked his bags.

Mudd's tragic story comes directly from the book – but with a couple of important differences.

Firstly, there is the way the story is told. In the TV series we see the events of Mudd's (Freddie Watkins) brief military career play out on screen in the present tense; but in the novel, Mudd's death is in the past and he is generally referred to as "the dead man in Yossarian's tent". It is only much later in the story that we learn his real name and what happened to him.

Because Mudd was killed in combat before he had even officially reported for duty, this unfortunate man's death has left him in administrative limbo. Heller writes: "The dead man in Yossarian's tent was a pest, and Yossarian didn't like him, even though he had never seen him. Having him laying around all day annoyed Yossarian so much that he had gone to the orderly room several times to complain to Sergeant Towser, who refused to admit that the dead man even existed, which, of course, he no longer did.”

Secondly, the TV series also adds another layer to the story which is not in the original.

In the novel, Mudd was sent on his first and final mission because "he had stopped at the operations tent to inquire the way to the orderly-room tent" and the military bosses consciously decided to put him in a crew straight away. He never met his tent-mates Yossarian or Orr before he was killed.

But in the TV series, Mudd only made that fatal blunder into the operations tent because of his new tent-mate Yossarian, who gave him the wrong directions. And he was only sent on the mission because the military bosses mistook him for someone else and wouldn't listen to his objections. Both of those details make his death seem even worse, somehow.

Catch-22 will air on Thursdays at 9pm on Channel 4