Peaks And Valleys, the new book by the hugely bestselling business writer Spencer Johnson, was written, we're told, "over the span of two decades". It's not clear what took him so long. This slim volume - subtitled Making Good And Bad Times Work For You, At Work And In Life - contains exactly 100 pages and uses very large type. At £9.99, that works out at 10p a page. The publishers seem to realise that readers might object to this, so they've designed the cover to include the slogan, "A gem - small and valuable!" as if it were a quote from a review. (It isn't.) The thinness, they seek to imply, is a selling point: here is not some complex self-improvement system but real wisdom, pure and straight from the source.

Johnson is best known for Who Moved My Cheese?, a "business parable" about change in the workplace that managed to combine a key Buddhist insight - that everything is impermanent - with the obnoxious implication that therefore you mustn't complain when your boss doubles your workload, halves your pay and forbids you from joining a union. Peaks And Valleys is a parable, too, though that label is perhaps unduly flattering: in a proper parable, a simple narrative illustrates a profound point. In Peaks And Valleys, an unhappy young man climbs from a valley to a mountain, where he meets a wise old man - there's always a wise old man - who essentially dictates to him the self-help book that Johnson would otherwise have written.

In Johnson's governing metaphor, peaks are happy, serene times, while valleys are periods when you're unfulfilled, unhappy and resigned to your fate. (Which is weird: in real life, valleys are verdant, while peaks are inhospitable.) Peaks And Valleys is being marketed as a recession-era book; Johnson knows many readers will be deep in a financial valley.

So what does he recommend? As with his earlier books, Johnson frustrates not because he's full of nonsense, but because he's so nearly wise. Half the book is dedicated to the idea that "peaks and valleys are connected": that good times are defined in contrast to bad ones, and that a life of monotone jollity would be no life at all. ("The deeper that sorrow carves into your being, the more joy you can contain" - Khalil Gibran.) That's surely right. But Johnson can't bring himself merely to recommend that we get to know our sadness: that would be radical, which he most certainly isn't. Instead, he destroys his peaks and valleys analogy with a tritely upbeat secondary lesson: you can turn valleys into peaks just by finding the good in any situation, by "being of service" - which in Johnson's world-view is limited to working longer hours - and by envisioning a better future for yourself.

Think about this. If you turn valleys into peaks, what do you get? A plateau? Some hillocks? But it's not just a problem with the metaphor. Just as in Who Moved My Cheese?, Johnson has taken an insight that's true but revolutionary - and rather scary - and rendered it safe for corporate culture. After all, you don't want your workers exploring their melancholy. You want them striving obediently for promotions. The real message of Johnson's work requires not a mountain-climbing metaphor, but a nautical one: don't rock the boat.

oliver.burkeman@theguardian.com