By one of those productive coincidences, I saw the final performance of Nicholas Hytner's shattering production of Timon of Athens last week at the National Theatre, and then, two days later, sat down with my grandson and read Frank Cottrell Boyce's children's novel Millions from cover to cover in a day. The overlap was instructive, most particularly against the background of a US presidential election that had none of the vibrant optimism of the Obama campaign in 2008. That took place before the global financial crisis deflated confidence as well as budgets. The common denominator in all this is money, and the effect it has on our psyche.

Timon of Athens was once described by Professor Frank Kermode as the "poor relation" of Shakespeare's great tragedies. On the page, it reads like an abandoned draft, which is presumably why it is rarely performed. By setting his 2012 version in the City of London, amid the bling of boom and then the dust of bust, Hytner transformed what is usually deemed one of the Bard's most obscure works into a parable for our times.

Timon begins like the Prodigal Son, dispensing unearned largesse in a whirling world of City crooks, braying bankers, parasitic poets, and air-kissing artists. He ends up as a down-and-out, pushing a supermarket trolley laden with jetsam, sleeping on cardboard boxes in the street, and railing against humankind in general. His sudden death offers the blindness of tragedy rather than the dawning of redemption.

What is striking about his earlier spendthrift philanthropy is that he gives compulsively, yet never seems satisfied. And he does it all on what turns out to be credit, underscoring Karl Marx's reading of the play as an allegory of the inherent contradictions of capitalism. Timon's clear belief that money can buy friendship rather than mere fawning takes us into deeper psychological territory, but it ends in a kind of embittered despair.

Cottrell Boyce is more helpful and hopeful. Millions centres on two precocious brothers, Damian and Anthony, who discover a huge stash of banknotes thrown from a train by robbers, only days before all stacks of sterling are to be burned and replaced by the euro. The cash comes crashing through the roof of a cardboard hermitage that Damian - who is obsessed with saints - has built by the railway line, after their mother has died.

"Have you met a Saint Maureen?" the eight-year-old repeatedly asks the various saintly visions who appear before him. In contrast, his brother Anthony, aged 11, is consumed by consumerism, cash, house prices, estate agents, and the money supply.

But Millions is far cleverer than merely setting up a simplistic contrast between God and Mammon. The outcast Timon inveighs wildly and generally against the dehumanising impact of money, which perverts and discourages the development of true virtue.

In Millions, the cash corrupts everyone who allows him- or herself to be seduced by it. Even the high-minded Mormons on the boys' estate are toxically tempted to greed, when Damian, hearing that they are Latter-day Saints, pushes thousands of pounds through their letterbox, assuming that they will use it to help the poor. Money brings out something predatory in us, but, in the end, we prey on our inner selves.

Yet, redemptively, the main characters in Millions have, deep inside them, a decency that allows them, clear-eyed, to pull themselves free of the lure of the lucre. Cottrell Boyce is an altogether more Christian writer than Shakespeare. There may be, he acknowledges, a polarity between spirit and Mammon, but there is a bit of both in all of us - and we can choose between them.

Paul Vallely is associate editor of The Independent.