Since the publication of his debut novel, Generation X, in 1991, Douglas Coupland has consistently proven himself to be a writer with plenty of ideas, as well as one keen to use experimental frameworks to express those ideas.

When this experimentation works, he seems highly adept at nailing the zeitgeist and the dysfunctions of pop culture. But his postmodern stylings don't always hit the mark.

The Gum Thief is Coupland's 12th novel, and sees him employing a fairly conventional, by his standards, conceit: the novel within a novel. It's a strangely confused book, which tackles his usual theme of alienation within the vacuity of modern living, but he also seems to want to say something deeper about the nature of writing and narrative, something he doesn't quite pull off.

The story revolves around two disaffected characters, struggling through life as they work in their dead-end jobs at Staples, a giant office supply store. Roger is 43 years old, divorced, alcoholic and still mourning his dead son. Bethany is a goth girl 20 years his junior who has turned away from the world because of a litany of painful deaths among her family and friends, and a mother she can't relate to.

Through a rather convoluted plot twist at the start, the two begin leaving notes for each other, communicating through letters all the thoughts and feelings they could never say to each other's faces. At the same time, Roger is working on a novel with the ridiculous title of Glove Pond, which he shows to Bethany for feedback.

Glove Pond deserves a mention. A dreadful reworking of Who's Afraid Of Virginia Woolf?, it features an ageing actress, her has-been author husband, the new hotshot novelist in town and his glamorous brain-surgeon wife. It's deliberately terrible, a kind of hapless mimicking of the likes of John Cheever and Raymond Carver.

While all this is good fun early on, with characters drinking themselves stupid and coming up with endless witty barbs to cover their deep loneliness, the joke wears thin after a while and the final sections of Glove Pond are a struggle to get through. Also, the point of the novel within a novel seems to get lost about halfway through, as if Coupland has run out of steam and can't work out what he wants to say with it.

Much more intriguing are the dialogues between Roger and Bethany. Although there is no great distinction between their voices, both are self-effacing, self-aware and ironically amusing, despite being haunted by depression and disillusionment.

Indeed, a feeling of apocalyptic nihilism threads through these passages, where one or other of them is forever doing something such as imagining waking up to find that everything living has died, or trying to make planes fall from the sky using the power of thought. But for all that, both Roger and Bethany are sympathetic characters, and when Bethany heads off for a disastrous trip to Europe, Fedexing her letters back to Roger, you genuinely feel for her as she mopes around the streets of Paris and London.

One structural problem is that Coupland has to give up on using just these notes between Roger and Bethany. Realising the restrictions of the set-up in moving the plot forward, he starts to introduce notes from other characters - Bethany's neurotic mother, Roger's ex-wife, a co-worker at Staples - which inevitably dilutes the effect.

This stream of first person narratives does at least allow for some trademark Coupland rants on technology, the environment and modern social mores. Indeed much of the prose here has plenty of verve and is extremely readable (the deliberately clunky passages of Glove Pond aside) which only adds to the disappointment that Coupland hasn't done more with his original premise.

It's perhaps churlish to complain when a writer like Coupland continually tries new things, but experimentation for the sake of it, especially when it peters out as in The Gum Thief, isn't always enough.