Overlooked classics: Nothing But Blue Skies by Thomas McGuane

When someone comes to the end of their marriage and describes it as an "anti-synergistic situation" your first assumption is probably not that they're a Montana cattle rancher with a habit of getting into bar brawls. But that is exactly what Frank Copenhaver, the midlife crisis-stricken anti-hero of Thomas McGuane's eighth novel, is. Over the course of his a 40-plus year career, McGuane has consistently confounded expectations of what an outdoorsy, western novel should be. In Montana, where he's lived on his own ranch since the late 1960s after moving from his native Michigan, he's surrounded by schmaltzy, whimsical fiction writers who mythologise the west: novelists who, in his own words, would never write "a scene where somebody was delivering a pizza". His rugged protagonists are more angst-ridden and prone to overthinking – beefier, slightly-less-wise-cracking Woody Allens who often happen to drive pick-ups. "It's not my job to put a smile on your face; that's the job of your bartender or pharmacist," he told the Guardian in 2007. If so, he's not quite doing his job right: Nothing But Blue Skies will often raise an (admittedly slightly uneasy) grin. How can it not, when it features a character who has made the mistake of "marrying three duck hunters in a row", or such wisecracks as "Shorty didn't need to shave because the cat could lick his beard off"?

When Nothing But Blue Skies opens, Copenhaver has broken up with his wife, Gracie, and "something has come completely loose inside". When he thinks about her potential new lover, it feels to him like seeing "a drooling new face at Mount Rushmore". He consoles himself by spying on her best friend from a tree as she gets undressed, then sleeping with her. But the initial freedom that comes from the split soon turns into a consuming, directionless emptiness. His business collapses, and he starts to feel the fear of spending his life alone, the full realisation that perhaps he's no longer meant to be someone's. "Loneliness – its not like other things that strengthen you," writes McGuane. "Loneliness makes you weaker, makes you worse. I'm guessing enough of it makes you cruel."

McGuane's own background contains a fair share of carousing, particularly alongside his friend Jim Harrison during the 70s, when he wrote screenplays (most infamously The Missouri Breaks, starring Marlon Brando and Jack Nicholson) and got married to Margot Kidder (his second marriage of three). And Frank, similarly, has spent time in California in his youth, where "everyone seemed surrounded by quotations". Back then, his father wrote him off as a drunken sports lecher, but, between the numerous erections he experiences during Nothing But Blue Skies and makes little effort to conceal, Frank is prone to strange bouts of sensitivity, unexpected in an alpha male outdoorsman. He clashes with the cowboys who work for him, one of whom runs over his beloved dog ("Dog ain't got no business under a tyre," is the employee's shrugging response) and another one of whom beats his wife and is memorably described as "as kind to cows as he was unreasonable with people". Frank is a man of simple desires – fishing, sex – but he's also thoughtful and introspective: much more so than the men who surround him and offer such nuggets of life advice as "the lady doesn't marry the carpenter unless he's got a second home in Santa Monica or a two foot dick".

Nothing But Blue Skies is not a novel that reads at pace. Some of its slapstick comic scenes – the bar brawl, a crash involving a forklift log skidder – are almost worthy of the brilliant Richard Russo, and it tends to luxuriate in them and in its setting, but you wouldn't quite call it a "hangout book": it's a little too tinged with despair for that. It was written in the early 1990s, just as the 1960s generation were coming to terms with the fact that they weren't going to live forever, and what seems to be really getting to Frank, as much as the collapse of his own marriage, is what he calls "the escalating boredom of life in the monoculture". He laments the new construction surrounding him, the music of his daughter's generation, listens to old Neil Young songs, wonders where the tone of apocalypse within them went and mourns the loss of the highs that drugs gave him in the early 70s. These are familiar themes now, but it's fascinating to witness them being voiced by a character who's not, say, a bohemian in Manhattan or a screenwriter in California, and to watch them being played out against a stunning big-skied backdrop: a place whose "rhythmic hills" betray "sea floor origins". As much as it confounds the tradition of western novels, Nothing But Blue Skies probably confounds the tradition of aging baby boomer novels even more.