The title promises "brief answers", and the (German) blurb claims said answers are "accessible and clear". Unfortunately, the answer are neither brief nor accessible.
The book is a compilation of texts from Hawking, begun during his lifetime and finished posthumously. The patchwork nature of the book shows, unfortunately, as several thoughts or explanations (such as about the dangers of artificial intelligence or the components of DNA) are repeated multiple times throughout the book. Overall, much of the writing seems incoherent, with sudden, unexpected tangents to different topics. Many times, Hawking's "brief" answers go on for well over 20 or even 30 pages, and I am left thinking that the answer could have been summarised within 10, had it not been for several off-topic passages.
The answers themselves are hardly suitable for the kind of layman the marketing suggests they were written for. Complex theories and concepts are presented with little explanation, and often, the explanation is inadequate. Hawking presents a theory, spends a short paragraph explaining it, then moves on to three new theories based on the first one, while I'm still trying to wrap my head around his first paragraph. I gave up any and all hope of understanding a single word he said about thirty pages into the book and didn't regain it until the end. I am left none the wiser, with the possible exception of a few personal anecdotes which are of little to no interest to me.
The one part that can be understood quite easily is near the end, when Hawking begins to lecture - or preach, rather - about the future of humanity in general, and various technologies in particular. Here, he repeats several inaccurate statements about the state of the world, which rather makes me wish he had stuck with cosmology. He parrots the myth that Earth is at risk from overpopulation and fails to see that the issue is not too little supply, but the way the supply is distributed. He entirely avoids any sort of analysis on the connections between climate change/food crises/resource scarcity/etc and capitalism, but rather preaches individual responsibility.
The fact that my owning or not owning a car (I don't) is irrelevant when compared to 70% of global CO2 emissions being caused by the super rich matters little to Hawking, nor does AI-based discrimination and undermining of worker's rights stop him from promising a world of total equality brought to you by AI. The racist myth of overpopulation is constantly repeated throughout the last third of the book, and whenever he is not busy praising Elon Musk - notable for market manipulation, discriminatory workplace practices, and subpar quality e-SUVs -, Hawking advocates wasting further money on space exploration.
Speaking of which: space exploration. If Hawking is to be believed, in space lies the future of humanity, liberation from all that plagues us, and our future as a species. Private spaceflight is something he can't praise enough, entirely unconcerned by the for-profit nature of the industry, it primarily being a hobby for billionnaires, the waste and pollution problems associated with it, or the socio-economic implications of an industry that's on course to divide humankind into a class that can afford to escape the confines of our planet and one that can't. One is tempted to remind Hawking of Nietzsche, who urged "remain faithful to the earth and do not believe those who speak to you of extraterrestrial hopes! They are mixers of poisons whether they know it or not."
Hawking seems downright obsessed with the idea of colonising our solar system, and it appears that as far as he is concerned, we can't leave Earth soon enough. Concerns of human rights, exploiting capitalists, and the likes among the stars are not something the great man appears to bother with (unlike Musk, whom Hawking loves to praise, and who recently publicly dreamt of luring workers into indentured servitude on Mars). In space, so Hawking, humankind could evolve, progress, and whatnot. Plenty of similarly vague promises and hopes are thrown around by Hawking, yet he fails to deliver anything concrete, just as he fails to think outside the capitalist box when he talks of financing space exploration, so-and-so many percent of the GDP to be dedicated to rockets and probes, and downplays the enormous costs of such programmes. An explanation as to why a moon base, or an outpost on Mars, would benefit humanity beyond lining the pockets of Elon Musk and satisfying human delusions of grandeur, Hawking has not.
He fails to deliver on his other big topic as well: artificial intelligence. On more than one occasion, he invokes Moore's Law (the processing power of computers doubles every 18 months), yet fails to account for the commonly accepted (including by Gordon Moore) assumption that Moore's Law will lose its validity around the mid-2020s as the limits of silicon-based processors are reached. So far, no viable quantom computer alternative appears in sight, but Hawking does not falter in his doomsday predictions of an all-dominating AI. In this, he sees the biggest threat to our continued existence - bigger even, it seems, than climate change, which, by the way, he hopes to combat by means of nuclear power. The ever-repeating warnings of an AI singularity (again, the editors appear to have stitched together several texts without editing out repetitions) grow boring fairly soon, and do little to lend credence to any of his prophecies. He would have been wise to take his own advice: that predicting the future is, while possible in theory, impossible in practice.
What remains, after all? A book that will leave newcomers utterly confused and none the wiser, and will likely not hold anything newsworthy for people familiar with the subject; perhaps a bitter aftertaste and the unfortunate impression that a great man's name has been slapped on a patchy manuscript in order to sell some books. Stephen Hawking may have been one of the greatest minds in recent history, but if this is truly his writing and not the doing of an untalented editor, then he was not a great teacher, and certainly not a particularly gifted philosopher. Perhaps the late and great man should have left guidance about the future of humankind in someone else's hands. And seriously, what's with all the Musk shilling?