It's not all fashion, films and fun as Jim Chapman reveals serious family stuff and his love of scientific facts in his first book.

It began as a list of camping essentials (plus a girlfriend who was brilliant at creating make-up tutor movies), and became a whirl of film premieres, fashion shows, product launches and international travel.

Jim Chapman is a social media influencer with millions of followers on YouTube, Instagram and Twitter.

He is so famous that when he returns to Norwich, it is hard for him (and his equally well-known girlfriend, and now wife, Tanya Burr) to go out without being mobbed by fans.

MORE: Crowds turn out for YouTube sensation Jim Chapman at Norwich store

He makes videos about what he is wearing, or doing, or thinking. They are engaging, funny, chatty and clever. And so is the book he has just written.

From black holes to belly buttons and from grief to ghosts, 29-year-old Jim covers pretty much the whole universe.

'I love writing, I write a lot of stuff. It's been a real passion project,' said Jim. 'I have got a lot I want to say.'

With an online reach of more than eight million, there are also a lot of people keen to listen.

His book, 147 Things, ranges from the wonders of science and why humans talk, to his distrust of trampolines, and a love letter to his wife on the subject of clearing out the shower sink trap.

'The truth is, I barely get by as a functional member of society, but I do know a lot of weird things. I'm fascinated by this stuff because it throws into perspective just how wondrous life is. The sheer unlikelihood that any of it exists at all,' said Jim.

'A week after finishing the book I was ready to go back to writing. I write a column for GQ magazine, I'm currently working on writing a film and I would love to write a novel.'

With his own ordinary-guy to international-superstar story, stranger than a lot of fiction, he might not have far to look for inspiration.

Jim grew up near Attleborough with his mum, twin brother and two older sisters, and went to school in Old Buckenham, before moving to Norwich at 15. After sixth form at Notre Dame he studied psychology at the University of East Anglia.

As a child he had wanted to be a comic book illustrator; as an adult he had jobs in Norwich clothes shops, offices, and in the courts organising bailiff visits, while considering career options.

Then, packing for Latitude seven years ago, he made a video about going camping. (Rule one, pack a torch; rule two, know where your torch is.)

'I did it because my girlfriend, my wife now, suggested it. My job was really boring and I wanted to do something creative. I was only doing it to fill a gap.' But it gained traction online and as followers multiplied, so did the money he was able to make. 'I was at the right place at the right time,' said Jim. 'My life is manic but it could all dissolve. It's quite scary to find how far it's come.'

Still in his 20s, Jim has hosted red carpet interviews for film premieres including Star Wars; The Force Awakens. He was part of a boy-band which raised cash for Comic Relief and has travelled to Sierra Leone to highlight child labour and poverty.

As a child, holidays were in Essex. Now he regularly travels the world for work.

'This job has totally changed me. When I started doing this I was very shy. But you either don't do things because you are too shy or you just have to suck it up,' he said.

147 Things, by Jim Chapman, is published by Sidgwick and Jackson for £16.99.

Seven of Jim's 147 Things:

•Thing 8: Having a pet is really weird when you think about it

•Thing 16: My wife is brilliant to chat to when she's asleep

•Thing 37: No matter how big you are, you are never big enough to stand up to your mother

•Thing 45: If you've never experienced a broken heart, I suggest you hurry up. It's an educational experience.

•Thing 74: If there's one thing sharks are good at, it's making teeth; their skin is even made of them

•Thing 121: Banana-flavoured things taste like a species of near-extinct bananas.

•Thing 147: There is an answer to, 'What came first, the chicken or the egg?'