John Marsden had no biological children but raised generations of ...

"Does anyone read your letters or can I write anything I want?"

That question, from 15-year-old Tracey to her pen pal Mandy in John Marsden's 1991 novel Letters from the Inside, so captured my imagination when I was kid, I posed the same question to my own pen pal.

Her response was similar to Mandy's.

"What do you mean, does anybody read my letters?"

Marsden nailed the language of teenagers in the novel, the curiosity, the angst and, as I would later write about in my own book, what it's like when you're a young person who cares about another young person who is incarcerated.

Letters from the Inside resonated with me, spoke to me, had impact and as a consequence, Marsden's other books were ones I sought out as a young adult.

Marsden, the acclaimed multi-award-winning Australian author who sold millions of books, and school principal who founded two schools, has died. He was 74.

In 2004, journalist and author George Negus interviewed Marsden on George Negus Tonight on ABC TV and described him as "one of Australia's most simultaneously popular and controversial authors".

"With no children of his own, along the way, John has copped a fair bit of flak," Negus said.

"'Unqualified to write about or for teenagers,' some critics argue. 'A dangerous influence on impressionable minds,' say others.

"But despite the flak, he remains determined to give teenagers the opportunity to think and talk frankly about things like sex, depression and suicide, relationship conflict and even war."

In Letters from the Inside, Marsden wrote about juvenile detention — Tracey was writing letters from inside jail, and I can't remember any other books I was exposed to as a young reader offering that perspective.

Marsden wrote books that resonate with young people. (ABC News: Dave May)

Common among his novels — Marsden wrote more than 40 in his lifetime — are protagonists who are children and young adults with depth and strength.

Marsden gave his characters the type of agency and power he felt was beyond his own reach when he was growing up.

Born in Melbourne the third of four children, Marsden moved home every four years because of his bank manager father's work.

In 1956, Marsden's father was transferred to Devonport in Tasmania, where Marsden attended Devonport Primary School.

"I had the best and the worst of teaching there, really," he said.

"The best being Mrs Scott in Grade 4 who encouraged writing and creativity and created this wonderful warm and supportive atmosphere.

"And I really flourished in there and first enjoyed writing for its own sake, I guess, and loved reading all the time."

By the time he was 10, the family had moved to Sydney where Marsden attended The King's School, Australia's oldest independent school, for the remainder of his schooling.

"It was a strange place to be. It was a very complex place," Marsden said.

"It was an island of 800 teenage boys and a number of teachers, many of whom had been there for decades and some of whom were abusive and violent, and others were gentle and intelligent and liberal."

It was during these teenage years that Marsden came up with the idea of his bestselling Tomorrow series.

"I was 15 and sitting in school, fantasising about a world without adults, because pretty much all the adults I encountered were authoritarian, were not interested in fairness or justice, they lacked compassion, they lacked imagination and they were really a bloody nuisance," he told the ABC's Dave May and Richard Mockler on Throwback, a series revisiting the creatives who shaped Australian childhoods.

Marsden's seven-book Tomorrow series, starting with the 1993 novel Tomorrow, When the War Began, portrays the invasion of Australia by a foreign power.

It was adapted to film in 2010 and a TV series in 2016.

Tomorrow, When The War Began was released as a movie in 2010. (film-book.com)

On ABC TV's 2018 Q&A program Stranger Than Fiction, audience member Elishka Josipovic asked Marsden, a panellist, whether we'd raised a generation in fear of invasion through his Tomorrow series and movie adaptation.

"I hope not, Elishka" Marsden replied.

"It was written 20 or so years ago when no-one talked about the security of Australia.

"I wouldn't write that book now — not because of a societal view but because of my own horror at the way refugees who have come to Australia have been treated.

"When I see people who arrive here legitimately seeking refuge and shelter, and they are treated as the scum of the Earth and they are sentenced to awful detention and sometimes death by both major political parties without any apparent scruples or conscience … then that would put me in a very different position … because demonising people like that is unforgivable and it's disgusting."

Author Michael Mohammed Ahmad, also on the Q&A panel, pushed back.

"I remember growing up in the Western suburbs of Sydney where there was tremendous xenophobia towards Vietnamese-Australian communities," Ahmad said.

"With all due respect, the language of the book and the implications in the book genuinely impacted and damaged the lives of a lot of the young people that I grew up around.

"And for me, reading, it's not about the ability to put words together, it's about the ability to pull words apart.

"When I pulled the words apart in the Tomorrow series I did interpret a paranoid, white nationalist fantasy about a group of coloured people illegally invading this country, and I always find that narrative deeply ironic because that's what the white population did to the Indigenous population."

Marsden told Ahmad and the audience that he was fine with people reacting to his work in whatever ways they wanted to.

It's no reaction at all that would bother him.

"I'd rather have [criticism] than have a bland book that people read and forget," he said.

Marsden was the founder of two schools in regional Victoria where he served as principal — an alternative primary school, Candlebark School, in Romsey which he started in 2006, and Alice Miller School, an arts-focused secondary school in Macedon, which he opened in 2016.

Marsden founded and was principal at Candlebark School. (ABC News: Dave May)

Marsden told the ABC he started Candlebark after contemplating what a good school would look like, then coming to the realisation that he needed to start one himself.

"I'm very much driven by the fact that my own early years were so awful, so I have every sympathy with young people who are in similar predicaments," he said.

Marsden had six stepsons he cared for from his wife Kristin's previous marriage, but raised generations more.

I should know. I'm one of them.