If you came to Sam Neill’s memoir without knowing the first thing about it, chapter one would hold a terrible shock. It begins amusingly enough: a lovely anecdote about his daughter Elena being asked at school when she was little about what her dad does for work. “My daddy sits in caravans,” she says, an answer “both perceptive and entirely accurate” writes the actor, who then goes on to describe a life spent on film sets: sitting in trailers, reading the paper, having cups of tea, waiting for the magic moment when someone comes and says: “We need you on set, Mr Neill.”

The tone shifts to reflective. There’s a potted preamble on what it means to live a good life, thereby setting tone and topic for the book, there’s musing about why he’s even writing a book, about who will read it, then he’s sounding somewhat swan-songish. And then, there’s this:

“The thing is, I’m crook. Possibly dying. I may have to speed this up.”

As narrative set-ups go, it’s a hook all right. There are so many questions: is he OK? Will he be OK? Where will we be by the book’s end? Should you … cheat and skip to the last chapter to find out what happens?

But here on a blue February day in New Zealand’s Central Otago, Neill, 75, is his very own spoiler alert. He seems very well, although he admits to being a little frail as he sits on a sunlit porch talking about what he’s processed about not existing while surveying all that exists before him. The glorious bounty of his farm unfolds all around: rows of pinot noir grapes for his wine, vegetable beds, herb gardens, heritage apple trees, gooseberry bushes, the odd clutch of chickens and ducks, black-faced sheep and cows in the distance, and newly planted trees he wants to see grow to maturity.

“I’m not afraid to die,” he says, “but it would annoy me. Because I’d really like another decade or two, you know? We’ve built all these lovely terraces, we’ve got these olive trees and cypresses, and I want to be around to see it all mature. And I’ve got my lovely little grandchildren. I want to see them get big.

“But as for the dying? I couldn’t care less.”

* * *

Sam Neill has established one of the more eclectic acting CVs with more than 150 credits over five decades, from the early launching pad of My Brilliant Career (1979) with Judy Davis, to his breakthrough role as dinosaur detective Dr Alan Grant in Jurassic Park (1993) to Jane Campion’s The Piano (1993) and more recently the malign Chester Campbell in TV’s Peaky Blinders. He has a reputation as a genuine Mr Nice Guy and his friends are legion, firm, and not only stellar – yes, there he is on his much-loved Instagram feed (541k followers) with Jurassic Park buddies Jeff Goldblum and Laura Dern singing, ahem, not too badly – but he has a parallel life where farmers and winemakers are his world.

Celebrity doesn’t impress him much, and he’s studiously avoided it. In his local village of Clyde, the one-cop town five minutes from his farm where he gets morning coffee, heads don’t turn much. In Sydney’s Surry Hills, where he has a home and splits his time, he takes delight in telling people who think they might know who he is that he’s Matrix actor Hugo Weaving. He likes to talk to strangers; he doesn’t care if they know who he is or not.

“I have a number of friends who are real celebrities, you’d know who they are, and I wouldn’t swap my life for theirs for a moment, even though they’re immensely rich and, you know, immensely famous.

“There’s a complete lack of privacy for one thing, and privacy is very, very, very important, I can walk down the street in Surry Hills and get my coffee, and nobody bothers me, you know? And there’s no paparazzi. My life is my own.”

Some of it he cheerfully shares on social media – the art of entertainment, he believes, is an honourable pursuit. And he does entertain: farm life, ukulele crooning, his winemaking, japery with Jeff. He has his delightful Dr Dolittle schtick, frequently appearing with his farm animals, many of them rescue animals affectionately named after celebrities and friends. There’s Laura Dern (chicken), Kylie Minogue (duck), Helena Bonham Carter (cow), Bryan Brown (pig, female). During this interview, Bryce Dallas Howard, a resplendent ginger hen, pecks her way past and later Michael Fassbender, a rooster of regal bearing appears chest-first around a corner followed closely by three hens. “Fassbender, you big cock,” Neill laughs. “He’s so full of himself, he’s always got his girls following. But he is very handsome.”

In Did I Ever Tell You This? Neill shares quite a bit more of himself. Indeed he has laid himself quite bare and, like most actors awaiting the reviews, he wants to know how he did. As memoirs go, it is very funny and extremely entertaining, but with a judicious touch of poignancy. No self-pity here. He is an enormously good raconteur and also deliciously indiscreet in some of his tale-telling (co-stars behaving badly, take note). But still, he is careful with his private life. Details of past relationships are either omitted, as in the case of his most recent relationship with the Canberra press gallery journalist Laura Tingle, or referred to fleetingly as with his marriages to actor Lisa Harrow and to film makeup artist Noriko Watanabe. His four children and eight grandchildren appear as careful references to his life’s joy and great love.

It is a collection of actor’s stories, a story of family and friendships, of love and pleasure that he started jotting down while isolated in his Sydney flat having treatment for his cancer. The shock came in March last year: he had swollen glands while he was in Los Angeles doing press for Jurassic World Dominion, goofing around with his “idiot friends”. Within weeks he was in chemotherapy for stage three blood cancer, specifically, angioimmunoblastic T-cell lymphoma.

For some time the treatment appeared to be doing its job and the writing was a salve; the memories kept him company.

“I found myself with nothing to do,” Neill says. “And I’m used to working. I love working. I love going to work. I love being with people every day and enjoying human company and friendship and all these things. And suddenly I was deprived of that. And I thought, what am I going to do?

“I never had any intention to write a book. But as I went on and kept writing, I realised it was actually sort of giving me a reason to live and I would go to bed thinking, I’ll write about that tomorrow … that will entertain me. And so it was a lifesaver really, because I couldn’t have gone through that with nothing to do, you know.”

He insists it’s not a cancer book (“I can’t stand them. I am never going to read another bloody cancer book in my life”), but he characterises the topic as a “spiral thread” throughout the memoir, keeping the narrative bound. He writes these sections in the present tense and then it’s back to funny coming-of-age stories, tales from film sets, and nostalgic recollections of his early life as Nigel Neill, the shy boy with a stutter who went to boarding school at eight and changed his name to Sam at 12.

Reflecting on his life has brought the surprise of remembering so many stories, but also the succour of remembering the love of his parents, whose presence he still feels around him. And every decade of his life, he says, has been better than the last. Even this decade, when he has been so ill, and he has trod the fine line between solitude and loneliness.

“I mean, I can’t pretend that the last year hasn’t had its dark moments, but those dark moments throw the light into sharp relief, you know, and have made me grateful for every day and immensely grateful for all my friends. Just pleased to be alive.”

* * *

When the first round of chemo appeared not to work and things were looking grim, a new, “very expensive” chemotherapy drug was proposed. He signed a contract with the drug company that if he was still alive after four months, the treatment would then become free. (“Have you noticed I have a slight look of lab rat about me?” he jokes.)

At the time, Neill was the only person in New South Wales on it, and when he switched his treatment to New Zealand so he could be home for Christmas, he was the only person in the country. He has to have it monthly for the rest of his life, but it has worked, despite the fact that he feels “shithouse” for two days after every treatment and doesn’t feel like eating. “I’m not off the hook as such, but there’s no cancer in my body,” he says.

The Christmas just passed, then, was particularly sweet: “I’ve never felt so well or happy in my life, it was fabulous to be able to taste everything. The wine was glorious and the food was superb. I swam every day down in my dam, and it was the most marvellous time … I had my family and all the grandchildren. It was just fantastic.”

Joyous gratitude seems to be Neill’s default position now, but there is contemplation of the self and the cosmos too. The sound of death coming up the stairs has done that.

“It’s much easier to identify who other people are, but you hardly ever ask the question of yourself: who am I? You know, [when I was sick] I would look in the mirror and see a completely different person, not a hair on my head, no eyelashes, the beard had fallen off on a pillow somewhere in hospital. I was unrecognisable.

“I would look at this alien … Really? Is that you? So that begs the question, who are you? And so I had to think about that. I mean, it’s never really interested me to sort of reflect on myself. You know, sometimes you go, you fucking idiot, why would you do that? But that would be as bad as it would be.”

But he’s forgiven himself his flaws and is revelling in the “strong sense of being this little speck in the universe, of so little significance … but a unique speck”. The notion of the afterlife is ridiculous to him, so instead he lightly contemplates the notion of consciousness (“If it’s an illusion, I’m fine with that”), and the alluring idea of “dissolving and dispersing into the cosmos.

“I don’t mind that idea at all.”

• Did I Ever Tell You This? By Sam Neill is published by Michael Joseph (£25) and Text Publishing in Australia and New Zealand ($55). To support the Guardian and the Observer, order your copy at guardianbookshop.com. Delivery charges may apply.