Houston, we have a billionaire problem. There are 2,781 individuals in the world worth more than a billion dollars, according to Forbes, and together these people have a net worth of $14.2tn, roughly the GDP of the Eurozone. The US boasts more super-rich than any other country, including eight of the planet’s 10 richest men. (The top of the chart is all men, until you get to the L’Oréal heiress Françoise Bettencourt Meyers, at number 15.) All but one of these eight made their fortunes in the tech sector, and you’ll be familiar with many of their names: Musk, Bezos, Zuckerberg, Gates.

So what, you might say – there’s no law against getting filthy rich. These people have worked hard for their Gulfstream jets and frigate-sized yachts. But with great piles of cash comes great power, and too often billionaires find ways around our frail systems of democratic oversight. They dodge taxes, bend politics and the media to their will, create monopolies, and disproportionately damage the planet. The problem is only getting worse, since, as Thomas Piketty has pointed out, when the return on capital exceeds the rate of economic growth, big money grows faster than small money or no money at all. In 2024, according to Forbes, the billionaires are collectively $2tn better off than they were last year.

The context is auspicious, then, for Anupreeta Das’s book Billionaire, Nerd, Saviour, King. The former finance editor of the New York Times has investigated the life and wealth of the totemic founder of Microsoft, documenting Bill Gates’s rise from boy computer whiz to world’s richest man to greatest living philanthropist to – well, we’ll come to that.

First, a little disclosure. The Bill & Melinda Gates Foundation has supported the Guardian’s global development coverage for many years. Following this newspaper’s tradition of editorial independence, I was primed, therefore, to cheer every swing Das takes at Gates and his dreadful money. Instead, I found myself inwardly trying to defend him.

The book sets itself up as an exposé of the billionaire’s life and secrets, his “hidden truth”, as the subtitle puts it. In fact it’s only loosely a biography, as Das interweaves the Gates story with passages of social commentary under subheadings such as Myths of the Nerd Ecosystem. Sometimes, these digressions incorporate interviews with people who seem to have only a tangential relationship with the subject. A section on anti-vaxxer Gates conspiracy theories, for instance, begins with the thoughts of an amateur artist in Spokane who thinks the billionaire’s dress sense makes him untrustworthy. Why? Because he can afford more expensive clothes and should wear them. Hmm. Das doesn’t even open or close with Gates, but bookends the volume with the complementary chapters Why We Love Billionaires and Why We Hate Billionaires, which set out America’s centuries-long obsession with wealth and how it’s ruining the republic. It’s hard to disagree with this stuff, but it’s very generic. Where’s Gates?

Here he is, in chapter two. It’s 1975, and a pair of young men – Bill and his school pal Paul Allen – are huddled in the blue light of their computer screens in the early hours, chugging sugary drinks and writing the first lines of code for the company that will become Microsoft. At last, a sense of the extraordinary life that is to unfold. But then we rapidly pull away, as Das devotes the better part of the chapter to nerdism and its social implications. “Who is a nerd?” she asks, before concluding that he is a young, white, solitary male, who often displays traits associated with autism. The dominance in the early tech industry of such people, who were “all on the spectrum”, as one interviewee puts it, discouraged others who weren’t white, solitary, geeky, or male, Das tuts. It’s hard to fault the logic, but was this all Gates’s fault? Plus, if this is the way we’re judging history, could we find a few lines to celebrate a triumph for the neurodiverse, instead of viewing them entirely as a negative? And can’t other genders and ethnicities in fact be “nerdy” too?

We grind on. Microsoft blossoms. Gates is America’s youngest billionaire at 31, a tech rock star. Of course he remains deeply “nerdy”. We linger on his terrible clothes, his greasy glasses, his bad hair and his dreadful conversation. But he is scarily authoritative, Das finds – the word “imperious” appears four times – and attends to every detail. He grows Miscrosoft using the kind of sharp practices big corporations seem to favour, buying out the competition or excluding their products from his software platforms. Soon Gates is synonymous with the 19th-century “robber barons”, who did anything to protect their monopolies. In the 1990s, antitrust legislation – the very laws that were written to control the barons – is used against Microsoft, by which time Gates has become a PR nightmare, the unacceptable face of US capitalism. So he moves away from the company, and instead he and his wife, Melinda, decide to save the world. They launch the Gates Foundation, applying the sorts of data- and results-driven practices at which Bill excels. He persuades other billionaires to pledge money, too. Soon they are running one of the largest private philanthropic enterprises in history.

Here, surely, some credit is due. The foundation and the Gateses, always hands on, have prevented millions of deaths, pumping billions of dollars into fighting Aids, tuberculosis and malaria around the world. They co-founded Gavi, the Vaccine Alliance, which vaccinated half the world’s children. It’s telling that during Covid, while another billionaire stood in the White House telling Americans they might cure the disease by ingesting bleach or by somehow bringing “light inside the body”, the Gates-backed Covax partnership was spearheading the global vaccination effort, procuring more than 1bn doses for people in poorer countries. But this doesn’t seem to wash with Das, who reports that the foundation is “bigfooting”, “neocolonial”, “antidemocratic”, and “top down”, and sees it as an egotistical way for Bill to charity-wash his reputation.

Wearying as these attacks are, concerning material follows, which relates to Gates’s contacts with Jeffrey Epstein. In 2019 it emerged that he had met the financier on numerous occasions between 2011 and 2014, which was after Epstein had served time for soliciting prostitution, including from an underage girl. Gates, who was introduced by employees at his foundation with the aim of raising funds, has admitted it was “a huge mistake” to spend time with Epstein. When the meetings came to light, Gates’s sex life was pored over. He acknowledged having an affair, and was reported to have been flirtatious and made advances towards colleagues, although he was “far from predatory”, according to a former Microsoft executive, and “not Harvey Weinstein”. Das calls him a “womanizer”, and notes that Melinda left him two years later, in 2021, which the author pointedly finds suspicious.

Who knows, the Epstein affair may one day finally do for Gates. But Das has found no new smoking gun, and her summation of him, as a man who switches between “entitled hero” and “hubristic villain”, but is at heart “a protean creature, a Zelig who … has leveraged his money and his fame to go from one guise to the next”, is overblown. The penultimate chapter is titled Cancel Bill, and that’s what the whole book feels like: an appeal to public opinion to write Gates off. As yet, and in the context of what other American billionaires do and get away with, it seems a little unfair.

• Billionaire, Nerd, Saviour, King: The Hidden Truth About Bill Gates and His Power to Shape Our World by Anupreeta Das is published by Simon & Schuster (£22). To support the Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply.