Glasgow, the late 1970s. A woman is busy cranking out copies of her teenage son's latest creative work on an old copier, blissfully unaware that they will one day be collector's items. The boy is called Grant Morrison and a faded copy of this old fanzine, called The White Tree, recently sold on eBay for more than £100.

"It's ridiculous!" laughs Morrison, who went on to be the writer of comic strips Batman, Superman and The X-Men, among others. "The first one was printed on, you know, those Banda copiers." He smiles. "It was steampunk technology. They did weird copies that came out in blue ink. It would fade over time. Every subsequent issue [of The White Tree] was done by my mum, up in the typing pool. She'd do like 150 issues of this thing. But honestly, all I really remember of that magazine is that I drew a barbarian girl on the cover of issue three. And she had a fur bikini on."

The women in the typing pool, he adds, confused her swimwear for something else. "All the girls were saying, 'What kind of muff is that?' I was mortified, a 16-year-old boy. 'Oh god,' I thought. 'What have I done?' I went back and painted in this huge kind of skirt thing – with a skull on the front. So there are two versions."

It was a fitting beginning, perhaps, for the writer of The Trial of Diana Prince, as Morrison's forthcoming Wonder Woman graphic novel is called. It's already causing much debate among comic fans, not least because Morrison has chosen to restore some of the original story elements to his Wonder Woman, or Diana as she's known to her friends. So what's the trial about?

"I thought: that's Wonder Woman's condition," says the writer, who is this week appearing at Stripped, the sizeable graphic novel arm of the Edinburgh book festival. "She's always on trial. It's like, why isn't she good enough, why doesn't [the comic] sell enough, why isn't she representative of this or this or this? And so I thought, 'Wouldn't it be great to just base the story on an actual trial – have the Amazons put her on trial, and tell the origins story via that.'"

Lynda Carter as Wonder Woman in the 1976-79 TV series. Photograph: Everett Collection/Rex Features

Wonder Woman, for those not in the know, is an Amazon warrior princess, known in her homeland as Diana of Themyscira. Dreamed up by US psychologist and writer William Moulton Marston in 1942, the superhero's interests are justice, love, peace and sexual equality. To help her achieve these goals, she has a boomerang tiara, indestructible bracelets and a lasso of truth (Marston also invented the lie-detector test). She occasionally flies an invisible plane, too, presumably being careful to remember where she parked it.

Morrison spoke to me briefly about Marston at last year's book festival. "William Moulton Marston was basically a kind of proponent of free love," he said. "So he and his wife had a lover called Olive Byrne, an 18-year-old, and Olive was the physical model for Wonder Woman. They created the character because they felt Superman represented a kind of blood-curdling masculinity. They wanted to introduce somebody more feminine."

Marston had some other colourful kinks: "He had this idea that the world would be better if men would just submit to women's complete instruction. But he took it all the way – not just submit to instruction but get collars on, and get down on all fours, and just admit that's where you belong, guys. So a lot of the Wonder Woman stories had this thread through them, this idea of bondage. But Marston called it 'loving submission'."

In one episode, Wonder Woman rescues some girls who have been enslaved by a Nazi: "The slave girls don't know what to do. Even though they've been rescued, they kind of like being slaves. So Wonder Woman just says, 'Oh, don't worry, you can be slaves on Paradise Island and one of our girls will take over. But she'll be really nice to you – unlike the Nazi!' And that was the resolution to the story."

Steve Trevor, the military man and love interest who lands on women-only Paradise Island, will feature in the trial in Morrison's version. "Steve takes the stand and speaks for men about women – he's the first man allowed on this island and he goes, 'OK, here's what we think.' Also, without giving too much away, this let me explore the differences between what a trial convened by society of enlightened utopian women would be – as opposed to what we think of as a trial."

What with the stampede of male superheroes to the big screen over the past two decades, Wonder Woman has seemed a bit of an also-ran (Joss Whedon's movie about the superhero never made it to the screen). Morrison seems just the man to fix such a state of affairs. The writer, who these days concentrates on the story and leaves the art to others, has even taken inspiration from Beth Ditto: the vintage character Etta Candy has been renamed Beth Candy and returned to her original curvaceous glory. "She's major and she's Wonder Woman's pal. I wanted to get in as many relationships between women as possible – there's Wonder Woman and her teacher, Wonder Woman and her mother, Wonder Woman and the girl she kind of fancies at school. I wanted lots of different female relationships to show that there's not just one type of woman and she's not representative of all women."

Is he worried about how fans will receive it? "It's a 120-page book – if they were seeing it in pieces, they would get really mad at me. It's quite provocative. But if you read all 120 pages, it's totally self-contained, it makes sense. So I'm hoping people will respond to it as a complete piece."

If The Trial of Diana Prince does cause controversy, it won't be Morrison's first. He once joked about running over Mark Millar, his fellow Scot and fellow comic writer, who has worked on The Fantastic Four and Kick-Ass. Many chose not to take it as a joke. And the first thing Morrison did when he started writing Batman in 2006 was give the Dark Knight a secret murderous ninja son. Later, he also made him fight the devil.

Action Comics: Superman, written by Grant Morrison (detail). Photograph: DC Comics

"It gets me down a lot," he says. It has been a difficult year for the writer, with personal losses and an end to his seven-year run on Batman. "It's been one of the most horrible years of my life. My mother died a few months ago and, two months before that, my cat died. It was born, kind of, in the pages of The Invisibles [Morrison's series about a secret organisation battling psychic oppression] back in 1995. He'd sit with me on the desk and sing along when I was playing the guitar. That was really heartbreaking.

"And then, two months later, my mother dies, not necessarily unexpectedly, but a lot faster than we had anticipated. So yeah, it's been a very strange year. I ended Batman as well, and I finished Superman. Now, I get up every day and do projects I'm totally into, that don't have deadlines. It just feels amazing. It's like being back doing the stuff I did when I was a teenager. It's just great."

Those early works, from Gideon Stargrave to Captain Clyde, are sadly unavailable in print today, but one particular title from the late 1980s made headlines earlier this year. Rebellion, the publisher of 2000AD, announced it was planning to reprint Zenith, Morrison's subversive superhero strip. Shallow, sarcastic and frequently used as a way for Morrison to criticise the Conservative party, the hero's five-year run in 2000AD ended in 1992. Zenith has been out of print ever since, due to a legal dispute over who owns the rights. So Rebellion's announcement of a £100 preorder-only hardback complete collection raised rather a lot of eyebrows, with Morrison unable to comment. But, choosing his words carefully, the writer is now able to talk a little about what's happening.

"Well, it's very simple," he begins with a wince. "We, uh, we spent five grand on lawyers' fees. They sent [Rebellion] letters. We were very keen to discuss it and we've never heard back from them. All I can say is that we tried to get into a discussion with them and they just didn't reply. I don't know what to do at this stage."

He seems genuinely upset, not least on behalf of those fans on a tight budget who will find £100 rather stiff. Still, there is plenty to be upbeat about. Wonder Woman is nearing completion, and a new DC Comics project called Multiversity is in the pipeline; it will feature, among other things, a black Superman. And the final part of Seaguy is due next year. "It's honestly the best I've ever written," says Morrison of the scuba-suit-wearing superhero with no superpowers. "It never sold well, but it's my thing. I want Seaguy to remain as my statement about life and death and the universe." Given that, until recently, Seaguy had a cigar-smoking tuna fish as a sidekick, this is no ordinary wish.

• This article was amended on 22 August 2013. The original subheading described Wonder Woman as "the Amazonian".