Publishers are normally so desperate to have their new books reviewed that they’ll bombard newspapers, websites and magazines with unsolicited pre-publication copies to garner coverage when the titles are launched. Just look at the Physics World filing cabinet: it’s full of books we didn’t ask for but were sent on spec by publicity-hungry publishers. With Stephen Hawking’s latest – and final – book, however, something very different happened.

To get a preview of Brief Answers to the Big Questions, which is released today, the publishers John Murray made Physics World jump through various hoops. Having done so, I was expecting great things of the book – and I can imagine many readers will too.

Hawking’s first popular-science book, A Brief History of Time, has sold more than 25 million copies since it came out 30 years ago and every further title he’s written since then has been a publishing sensation. His latest book is bound to be huge too. Indeed, I can imagine a cottage industry of “lost” or unfinished Hawking books and papers being published for decades, just as they have with the works of that other great superstar physicist Richard Feynman.

Hawking was still working on Brief Answers to the Big Questions when he died last March. To fill the gaps, the publishers decided to draw on Hawking’s “enormous personal archive” of responses he’d given as speeches, interviews, essays and articles to the many questions people had asked him. The book was then completed in collaboration with “his academic colleagues, his family and the Stephen Hawking Estate”. A percentage of the royalties are earmarked for the Motor Neurone Disease Association and the Stephen Hawking Foundation.

So what of the book itself? It’s divided into 10 chapters, each posing a different question. Three are open-ended: “What is inside a black hole?”, “How did it all begin?” and “How do we shape the future?”. The other seven are all yes/no questions, such as “Is there a God?”, “Is time travel possible?” and “Will we survive on Earth?”, all of which seduce the reader into thinking there will be easy answers. Except, as you might expect, it’s not that straightforward.

Take the chapter on “Can we predict the future?”. Starting with regular astronomical events, it swiftly moves on to scientific determinism, quantum physics, hidden variables and Heisenberg’s uncertainty principle. Under the guise of a simple question, Hawking has managed to take the reader on a whistle-stop tour of the quantum world (bottom line: no we can’t predict everything). It’s a clever ruse. Ask a simple question and you’ll draw in readers who might otherwise not know they’d be interested in complex science.

Hawking ticks off all the big ideas you’d expect from one of his books. General relativity. The Big Bang. Inflation. Galaxy formation. Gravitational waves. Matin Durrani

Elsewhere, Hawking ticks off all the big ideas you’d expect from one of his books. General relativity. The Big Bang. Inflation. Galaxy formation. Gravitational waves. There are also some niche topics too: imaginary time, M-theory and cosmic strings (although surprisingly nothing on dark matter or dark energy). The final three chapters touch on the future of humanity, the prospects for colonising space, and whether artificial intelligence will outsmart us (answer: probably, so we should embrace the prospect but plan carefully for any unwanted side effects).

One of the more accessible chapters is entitled: “Will we survive on Earth?”. It contains all the usual suspects that threaten the planet from over-population and nuclear weapons to global warming, terrorism and Donald Trump. It’s a sobering reality check, with Hawking predicting it as “almost inevitable that either a nuclear confrontation or environmental catastrophe will cripple the Earth at some point in the next 1000 years”.

I can imagine it must have been incredibly frustrating for Hawking to communicate, given that in later life he could do so only by twitching a facial muscle in response to a computer screen. This difficulty meant that anything Hawking said or wrote was concise and with no redundant words. It also made his spoken messages memorably pithy, especially as they were delivered in his trademark computerized and almost Delphic voice.

However, reading more than 200 pages of text in that style is hard. Ploughing through Brief Answers to the Big Questions is like eating a thick slice of rye bread. Good for you, but not that easy to digest and I kept craving a fluffy white croissant to leaven the pace. Actor Eddie Redmayne says in the foreword that Hawking was “the funniest man I have ever had the pleasure to meet” and I’d have liked more evidence to back up that claim. Redmayne famously got to know Hawking, whom he credits with owning a “pair of exceptionally expressive eyebrows”, while playing him in the 2014 Hollywood film The Theory of Everything.

There are some amusing moments. When Hawking went to the University of Cambridge in the 1960s, he originally wanted to do a PhD with the astronomer Fred Hoyle. But as Hoyle had enough students, Hawking was assigned to Denis Sciama instead. “It was just as well,” Hawking recalls, “because I would have been drawn into defending his steady-state theory, a task which would have been harder than negotiating Brexit.” (Hoyle famously argued that we live in a universe where matter is continually created.)

I also enjoyed Hawking’s sense of self-deprecation. To Hawking’s colleagues, he was “just another physicist”. But to the wider public, he claims to have been possibly the best-known scientist in the world. “This is partly because scientists, apart from Einstein, are not widely known rock stars, and partly because I fit the stereotype of a disabled genius. I can’t disguise myself with a wig and dark glasses – the wheelchair gives me away.”

I was left continually wondering if each sentence was what Hawking had said in the past or was something entirely new. Matin Durrani

The problem with these passages, as with the rest of the book, is that it’s not clear whether they are fresh or culled from the archives. To the book’s credit, the editing is seamless, but I was left continually wondering if each sentence was what Hawking had said in the past or was something entirely new. Short of combing through his past books or utterances, readers will just have to carry on regardless.

Hawking also loves to veer off-topic: no sooner has he tackled nuclear Armageddon than he’s onto infinite numbers of closed loops of particles, Planck lengths and DNA. Another problem is that Hawking didn’t begin at page 1 and write a coherent story that unfolds through the book. Instead, many chapters repeat points that went before, although it does allow each to be read pretty much independently.

This book will stand as Hawking’s manifesto. Optimistic, upbeat and visionary, it sees science – and scientific understanding – as vital for the future of humanity. Matin Durrani

With an entertaining introduction by Hawking’s US colleague Kip Thorne, who shared the 2017 Nobel Prize for Physics for the discovery of gravitational waves, the book concludes with a moving afterword from his daughter Lucy Hawking. In it, she recalls the events of his funeral on “the bleak greyness of a Cambridge spring day” and pays tribute to how her father “at the age of 75, completely para­lysed and able to move only a few facial muscles…still got up every day, put on a suit and went to work”.

Brief Answers to the Big Questions will appeal to school students, undergraduates and non-scientists with an appetite for the grand challenges in physics. Those who are more familiar with cosmology, relativity and astronomy will not find much that is new, although it is always interesting to see Hawking’s take on affairs. In essence, this book – especially the final chapter “How do we shape the future?” – will stand as Hawking’s manifesto. Optimistic, upbeat and visionary, it sees science – and scientific understanding – as vital for the future of humanity.

2018 John Murray 256pp £14.99hb