Four years or so ago, the oft-repeated story goes, Justin Vernon was holed up in a cabin in the rural wilderness of Wisconsin, recovering from a bout of glandular fever and the break-up of both his relationship and his former band, DeYarmond Edison, passing the time by tentatively recording demos. How things have changed: the trajectory that his career has since followed – essentially the equivalent of travelling at speed up a ski jump – has seen the resulting album, 2008's For Emma, Forever Ago, acclaimed as one of the first classic albums of the 21st Century, its songs scattered across the airwaves on hit shows like Grey's Anatomy, Skins and House, its standout track ('Skinny Love') covered by a 14 year old (Birdy) and taken to the upper reaches of the UK charts. And you know you've crossed over when you find yourself playing basketball in Hawaii with Kanye West while working on his forthcoming album, last year's My Beautiful Dark Twisted Fantasy.

So it's from an entirely different world that Vernon launches his second album - a record which, he conceded in an interview with Rolling Stone earlier this year, presented fundamental difficulties: "somewhere along the line," he said, "I forgot how to write songs". Fortunately it's a skill he seems to have recovered by recasting Bon Iver as a 'project' rather than a solo undertaking, working in a purpose-built studio close to his childhood home with a carefully selected cast of musicians that enabled him to change his 'role as author'. These, it has to be said, were more than mere pick-up musicians: amongst them were Greg Leisz (pedal steel player for Lucinda Williams and Bill Frisell), Colin Stetson (saxophonist for Tom Waits and Arcade Fire) and C.J. Camerieri (brass for Rufus Wainwright and Sufjan Stevens), as well as members of his live band, Sean Carey, Mike Noyce and Matt McCaughan. Certainly it's better company than the two deer he allegedly killed for food back in that cabin.

It's obvious very early on that Vernon is in no mood to repeat himself: 'Perth' opens with an electric guitar, and the acoustic strums that characterised For Emma... are largely absent. Carey's drums are also pushed way upfront, building from a military tattoo before they explode dramatically into life with burst of staccato fury that could almost be the work of Mogwai. 'Calgary' grows similarly into something that could help bring your average indie rocker onboard, a warm soft focus fuzz bleeding into the 80s synth pop sounds – not unlike Gayngs, with whom Vernon of course collaborated - that characterise its opening. 'Hinnom, TX' also plays with the same toys, Vernon's familiar falsetto replaced by a suave baritone, his tremelo piano tickled by bursts of static before those multi-tracked Bee Gees vocals return. 'Minnesota, WI' meanwhile rumbles into life with rolling toms and cinematic guitars before Vernon exercises that throaty baritone once more, a banjo plucked beneath the warm sounds of a chorus of saxophones and what can only be described as a 'phat' bassline. And though 'Holocene' and 'Michicant' see him return to more recognisable territory, the arrangements are again slowly bulked out, this time with the kind of instrumentation that helped make Talk Talk's later records so eerie, even if it never drifts into the more ethereal territory they explored.

There's something even more fascinating going on beneath the surface, however, and it's evidence that Vernon still seeks to keep the world at arm's length. He might have lost the privacy that Wisconsin cabin afforded him, and the songs may demonstrate richer, more accessible arrangements and a significantly more 'produced' sound, but Bon Iver is, lyrically, almost impenetrable. Any window into his soul has the curtains firmly drawn. Of course, Vernon's words have never been the most transparent – the fact that he inspired a young teenager to sing of "staring at the sink of blood and crushed veneer" is in itself notable – but here he seems to have amassed a vocabulary that appears not only deliberately archaic but at times of his own invention.

In fact, when faced by lines like "I'm tearing up, acrost your face/ Move dust through the light/ To fide your name/ It's something fane/ This is not a place not yet awake,/ I'm raised of make" – especially when they're an album's opening words – it's hard not to wonder whether he is in fact deliberately messing with his audience. It's as though he's so fearful of having the power to fill up arenas that he's making it as hard as possible for listeners to engage with the record textually, something further underlined by the manner in which he places stress on unfamiliar syllables within his chosen words. Not for Coldplay the lines "doubled in the toes annex it, it minute closed in the morning did not lose it in the stack's stow, imma lay that call back on ya", sung back to them by a mass crowd waving lighters in the air. And you won't hear Bono instructing his audience to "build your tether rain-out from your fragments... break the sailor's table on your sacrum... fuck the fiercest fables, I'm with Hagen".

It's as though there's only so much of his heart and soul Vernon can share, especially now he has such a huge database of fans likely to pore over every line he's written, and so he's given his all musically whilst keeping his feelings to himself. But it's not throwaway nonsense that he's crafted here: his text is so dense that it makes Seamus Heaney's poetry seem translucent. You've got to have a special talent to do that. Either that, or a particularly impressive collection of fridge magnets. The use of words like 'melic', 'clast' and 'latchet' is perfectly designed to prevent anyone infusing his lyrics with unintentional meaning, and though the chance remains that, to Vernon himself, they represent something significant, it's almost impossible to imagine that anyone else will be able to identify much sense in them.

Fortunately, what Bon Iver lacks in lyrically anthemic possibilities – in itself, it should be emphasised, probably a good thing – it more than makes up for with its emotional heft. It's peppered with goosebump moments, never predictable, ravishing in its sound and romantic in its intent. And, as if to emphasise that even within a forty-minute album Vernon wants to keep moving forward, it ends with a curveball: 'Beth/Rest' opens with a Korg piano that will sound familiar to anyone who grew up listening to Phil Collins and Bruce Hornsby, about whom Vernon once said, "I didn't even know that I was supposed to apologize for listening to [him]"), before Vernon's voice – vocodered, perhaps unnecessarily – starts swooping between Candi Dulfer saxophones and a guitar solo which went missing around the time Mark Knopfler was recording the soundtrack to Local Hero. It should be awful. But, frankly, it's not. Somehow it just makes you realise how grateful you are to Bon Iver for creating the space he obviously needs to use in whatever way he wants: rather than settling for a pale shadow of For Emma..., he's opted to challenge himself. We're all better off for that.