The best thing about Mike Wendling’s new book is the cover. It is extremely clever – a digitised, mashed-up, almost-but-not-quite swastika, which is both artistically striking and a reflection of the book’s central argument: that the “alt-right” represents a novel form of extreme rightwing thinking that is at once familiar and confusing.

Most people first heard of the “alt-right” around mid-2016, as the internet-savvy rabble that got behind Trump hammered out frog memes, worshipped Milo Yiannopoulos and loitered around the Breitbart website. No one was entirely sure whether this was a new combination of internet libertarians and youthful nationalists or simply old-fashioned racism repackaged. According to Alt-Right: From 4chan to the White House, it’s a bit of both and very hard to pin down: “an incredibly loose set of ideologies held together by what they oppose: feminism, Islam, the Black Lives Matter movement, political correctness, a fuzzy idea they call ‘globalism’ and establishment politics of both left and right”. Unsurprisingly, then, writes Wendling, “it’s a movement with several factions which shrink or swell according to the political breeze and the task at hand”.

To make sense of this confusing new amalgam, Alt-Right takes a long-lens look at the group. Early chapters on its philosophical inspiration will fascinate the general reader. The election of Barack Obama in 2008 helped fire up a small conservative fringe that were strict traditionalists on questions of gender, ethnicity, race and social order (some called themselves “paleoconservatives” and dreamed of an intellectual, anti-establishment, ethno-nationalist, youthful conservativism). One of these early followers was Richard Spencer, who would go on to become a leading member. Wendling is strong when tracing the movement’s roots. The section on “Gamergate” (the 2014 controversy over feminism and video games journalism) is probably the most succinct and accessible account I’ve read.

The wider story here is how a set of apparently fringe ideas barged noisily into the mainstream. To tell that, Wendling, a journalist who works for BBC Trending, has put in long hours on the countercultural blogs and forums where the “alt-right” lives. That means plenty of sharp insights: for all their chest-beating about liberal snowflakes and free speech, the “alt-right” are incredibly thin-skinned, being constantly outraged by social justice warriors, the mainstream media. Yet they also intentionally fall foul of speech laws or regulations so they can cry victim and whine about political correctness. Perhaps most importantly, they gratuitously offend and outrage and use that to show how easily people are offended.

Seasoned watchers of the “alt-right” will find much of the story familiar. This is clearly written for the general reader (and Wendling does a decent job of explaining niche internet culture without losing the pace – the bane of all tech writers). That means, however, that Alt-Right sometimes lacks the depth of analysis found in Angela Nagle’s Kill All Normies, which is something closer to an ethnography of the group. A slightly laboured chapter on language, for example, should have been bundled into an annex by the editor: it’s essentially 30 pages of definitions, which is out of synch with the otherwise upbeat prose. For a book aimed at a wide audience, it oddly avoids some of the broader context of why and how the movement arrived when it did.

“Twitter, of course,” writes Wendling, “allows this new breed of journalist-agitators to do their work and build their brand with amazing speed.” Absolutely correct, but the reader is left wanting more. He is too quick to discharge the idea that it’s partly a reaction to free-speech restrictions on campus, a self-righteous, pious commentariat unhealthy “call-out culture” and the growth of identity politics. How “mainstream media” failings, such as the liberal bent in most (printed) US news and the wild lunatic ravings of Fox News, have conspired to open a path for sites such as Breitbart would have been interesting from a BBC staffer. Perhaps that’s why he left it out.

The strongest sections are undoubtedly his own experiences, often resulting from his BBC reporting. There is a fascinating story of Wendling receiving a bomb warning from one “Australi Witness”, who turned out to be a young man called Joshua Goldberg. Goldberg spent most of his life online running an interlocking web of dozens of fictitious identities, and was ultimately convicted of attempting to blow up a building. Later, Wendling gets besieged with “alt-right” spam while on the social network Gab. He ventures offline too and hangs out with a fairly charming “ethnocentric nationalist”. The book is immeasurably helped along by these moments. Time spent with Lenny Pozner – whose child was murdered at Sandy Hook and who has been attacked by conspiracy theorists associated with shock jock Alex Jones, an “alt-right” hero – is especially notable and quite moving.

These personal moments all have a slightly sinister undertone when you read the acknowledgments. No names are mentioned – it’s all “colleagues”, “unsung heroes” and “researchers”. It’s easy to understand why.

The central question of Alt-Right is: who are they really? Is it an internet-based, troll-like movement of free-speech fanatics with a small fascist contingent or a bunch of Nazis who hide behind screens, bogus human-biodiversity science, free speech and irony? Wendling says it’s hard to be definite, but the reader is led to conclude it’s more the latter. To his credit, Wendling makes a strong case, documenting numerous ideological and personnel crossovers between the trolls and racists. I’m less convinced. Because of its ephemeral nature – the fact that thousands of uncensored posts from anonymous alt-righters (some racist, some troll-like, some neither) are available to researchers – and the group’s lack of formal structure or leadership, an equally strong case can be made for both.

This issue – who is in a digital movement and who is not – is now a preoccupation for all political parties. Is the antisemite with a Momentum Twitter handle the “real” face of Labour or is it the anti-antisemitic moderates? Is the Facebooker ranting “Enoch was right” the true Ukip or is it the principled libertarian such as former MP Douglas Carswell? Wendling doesn’t quite crack that puzzle, perhaps because it’s uncrackable, but more consideration would have been welcome. Similarly, Wendling argues that words can and do lead to sticks and stones and gives examples of where the online rage has prodded people into violence. However, there’s plenty of academic work that questions the causal link between words and physical action and Wendling might have usefully drawn on some of it.

These quibbles aside, anyone hoping to get a deeper look at the “alt-right” will find this accessible, enjoyable and informative. The best thing about the book is not the cover – it’s the content. I used that opening line as clickbait to grab your attention and provoke a response. You didn’t really believe me, did you?

Jamie Bartlett’s book, The People vs Tech, is published by Ebury (£8.99).

• Alt-Right: From 4chan to the White House by Mike Wendling is published by Pluto (£12.99). To order a copy for £11.04 go to guardianbookshop.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99