He might have a reputation for being cantankerous, but a letter has emerged online that reveals a softer side to comics heavyweight Alan Moore.

The Letters of Note website has published correspondence from 2013 between Moore, now 62, and a primary-school boy, then aged nine, who calls the writer of Watchmen and V for Vendetta “the greatest author in human history”.

Joshua’s letter to Alan Moore. Photograph: Provided by Joshua's family

Nine-year-old Joshua was taking part in a class exercise at his primary school, in Moore’s native Northamptonshire, in which pupils were asked to write a letter to their favourite author.

Joshua’s letter read: “I am writing because I want to know more about your comics including V for Vendetta, Watchmen, League of Extraordinary Gentlemen and Swamp Thing. I also want to say thank you for making such amazing graphic novels and how did you make such wonderful things?”

Joshua added that the first Moore book he read was V for Vendetta, about a masked anarchist in a totalitarian near-future Britain. He said it was “very cool when he blows up Parliament”. He also listed his favourite Watchmen characters in order: Rorschach, Dr Manhattan and the Comedian. (“I like the way he uses a flamethrower as a cigar lighter and a smiley face for a badge.”) The letter ended: “All in all you are the best author in human history. Please write back.”

Moore obliged: after initially saying his reply would be short because he was busy, he revealed he was “really pleased that you’ve enjoyed so much of my stuff, and especially because most of my readers these days are people almost as old as I am”.

Moore added: “Of course, I appreciate my audience however old they are, but it’s particularly gratifying to think that I’ve got intelligent and adventurous readers of your own age out there. It’s the kind of thing, when I’m taking my vitamin pills and swilling them down with Lemsip, that makes me feel like I’m still ‘down with the kids’.”

Quick Guide The five Alan Moore comics you must read Show V for Vendetta (1982 - 1989) This dystopian graphic novel continues to be relevant even 30 years after it ended. With its warnings against fascism, white supremacy and the horrors of a police state, V for Vendetta follows one woman and a revolutionary anarchist on a campaign to challenge and change the world. Superman: Whatever Happened to the Man of Tomorrow (1986) Moore's quintessential Superman story. Though it has not aged as well as some of his work, this comic is still one of the best Man of Steel stories ever written, and one of the most memorable comics in DC's canon. A Small Killing (1991) This introspective, stream-of-consciousness comic follows a successful ad man who begins to have a midlife crisis after realising the moral failings of his life and work. Tom Strong (1999 - 2006) A love letter to the silver age of comics that nods to Buck Rogers and other classics of pulp fiction. Tom Strong embodies all of the ideals Moore holds for what a superhero should be.

The League of Extraordinary Gentleman (1999-2019) One of Moore's best known comic series, The League of Extraordinary Gentlemen is the ultimate in crossover works, drawing on characters from all across the literary world who are on a mission to save it.

Moore also pointed out the necessity for any writer to be a voracious reader – “this is why libraries are so important” – and included some of his opinions about large comic book companies. Moore famously clashed with DC Comics over its perceived interference in his work, including their pulping of an entire run of The League of Extraordinary Gentlemen because of an advertisement for a douche by Marvel, their main competitor, in the background of one panel.

“Although I’m still very proud of the work that I did on all the books mentioned above, the fact that I no longer own any of those titles (I’m afraid they’re all owned by perhaps-less-than-scrupulous big comic-book companies) means that I’m always most interested in my most recent work, so I was glad that you’d liked The League of Extraordinary Gentlemen,” wrote Moore.

In addition to his reply, Moore sent Joshua a copy of the just published League book Heart of Ice, and some art by Kevin O’Neill for the then unreleased follow-up, The Roses of Berlin.

The back of the cover for Alan Moore’s Jerusalem, with Joshua’s quote at the end. Photograph: Knockabout Books

The author closed by telling Joshua that he has to get into Northampton to buy his wife Melinda a wedding anniversary present and said: “Thanks for calling me the best author in human history, which I don’t necessarily agree is completely true but which I may well end up using as a quote on the back of one of my books some day.”

Moore has kept that promise; his massive novel Jerusalem, which is published in September, will feature Joshua’s endorsement as a blurb.

The letter ends: “Take care of yourself, Joshua. You’re obviously a young man of extraordinary good taste and intelligence, and you confirm my suspicion that Northamptonshire is a county touched by the gods.” The sign-off is from: “Alan Moore. Best Author in Human History. In your face, Shakespeare, Joyce and Cervantes!”

The correspondence was passed by Joshua’s father to the Letters of Note editor Shaun Usher, who contacted Moore to get his permission to reproduce it.