【Watch Metamorphoses Online】

The Watch Metamorphoses Onlineworld's richest man made a $42 million investment in a vast clock, now under construction, that is designed to tick away for 10,000 years. Elon Musk sent a car to space that should orbit the sun for millions of years, containing a miniature library that will last for billions more. Meanwhile Netflix's latest hit, Altered Carbon, shows us a future where the rich live forever, albeit inserted into fresh bodies (aka "sleeves").

No doubt about it: long-term thinking is in fashion, at least among the nerds. These days, Silicon Valley is obsessed with legacy projects. Mark Zuckerberg wants to cure all disease before the 22nd century begins. The promise of expanding human lifespan in limitless directions is so close the billionaires can taste it.

But would you really want to live forever? What would it entail? How would you feel? Would it be a blessing or a curse? Will the heart ever let go of those it inevitably lost? For one well-considered answer, turn to Matt Haig's new novel How to Stop Time.

If you've heard of this British bestseller, published in the U.S. this month, that's probably because there's already a movie in the works -- courtesy of Benedict Cumberbatch, who will play its timeless hero, Tom Hazard. Darkest Hour's screenwriter is penning the adaptation as we speak. (Bonus of reading the book now: that delightful moment when the trailer drops and you're the one in the audience looking smugly knowledgable.)

Tom Hazard is timeless in the sense that he has a rare and seemingly beneficial disease. It causes him to age at a fraction of the rate of you or I; born in the 15th century, he is only now starting to look like a 41-year old.

As the book opens, Tom is done. He's out. He's had all the adventures you might expect; he's met Shakespeare and Captain Cook and F Scott Fitzgerald. He joined a secret society of Methuselahs who share his disease, and that took him around the world to either bring other long-lived newcomers into the fold or silence them permanently.

Quitting all that jazz, the eternal man becomes a high school history teacher in London. After he's been worn down by long emotional centuries, the only thing that can still reach Tom's broken old heart is flicking on the occasional light bulb above kids' heads in a classroom. (Teachers everywhere, take a bow -- you're in the one profession that doesn't get old.)

This premise is so perfect, the eternal and the mundane clashing in a London school, you can see why it was snapped up as a movie. I'll go further and say it would make a great serialized TV comedy drama: the kids keep wondering why teacher is exceptionally knowledgable about exactly how the streets around the school looked in medieval times.

Tom is the model of a modern Methuselah -- in that he's starting to spend a lot of time on social media. "It draws more suspicion not having a Facebook page than having one," he says, by way of explaining why that sinister secret society of his is cool with it.

It's also by way of subtle commentary on our culture, of which there is a fair bit in this first-person narrative. The 500-year-old teacher cannot help but lecture his readers; we'd expect nothing less.

Mostly, the lesson is about what a grind it is to live this long. Tom's heart is largely broken because his wife Rose died in the 16th century, and his daughter -- who also showed signs of the long-lived disease -- went missing at the same time. The promise of finding her is what kept him working for the secret society all those centuries.

Here's where readers will diverge, as there's rather a lot of flashbacks to Tom's life with Rose. If you're into the whole soft-focus romance thing and really enjoyed Shakespeare in Love, you'll appreciate these long chapters. But if you're in the flashbacks-bog-a-story-down camp, this may not necessarily be the novel for you.

But at least there's a point to flashing back. Which is that Tom is starting to find romance again, for the first time in an age, in that London school. Cue a lot of floppy-haired, Hugh GrantBenedict Cumberbatch-style bumbling around his new beau. Like I said, prime-time sitcom worthy. (But also the secret society forbade him from falling in love: cue the prime-time drama angle!)

For example, Tom is especially inept on social media and makes the classic mistake of hitting the Like button on his crush's Facebook post at 3am. Yeah, we've got no idea what that's about, I'm sure.

In an era where tech giants think about living forever while the rest of us mess around on Facebook, it's refreshing to see a narrative about a man who can do both.

But How to Stop Timeis also a considered, heartfelt document, as you might expect from an author who wrote an internationally bestselling memoir of depression, Reasons to Stay Alive. It unfolds its secrets carefully: an action-packed but often sad story for slow, long-term thinkers.

Wrapped inside this sci-fi school sitcom premise is a poetic manifesto of what really matters in the long run. One that Jeff Bezos, Elon Musk and Mark Zuckerberg would do well to read.