NOT a lot is known about the Dutch painter Carel Fabritius.

He was born in 1622 and died 32 years later in Delft, one of the many victims of a spectacular and catastrophic gunpowder explosion which destroyed a swathe of the city. At the time Fabritius was a student of Rembrandt and is deemed by connoisseurs to have been one of the great master's most gifted apprentices. Indeed, several portraits previously thought to have been by Rembrandt have been re-attributed to Fabritius.

The most famous of the few works of his which have survived is The Goldfinch, an exquisite miniature, which hangs in The Mauritshuis in The Hague, where it is invariably overlooked by visitors eager to view Vermeer's The Girl With the Pearl Earring. That, though, may soon change, now that Donna Tartt has made Fabritius's little painting the emblem of her new novel.

It is an irony too obvious to ignore that The Goldfinch of 2013 is not the novelistic equivalent of its seventeenth-century namesake. Tartt's novel, her third in 21 years, following The Secret History (1992) and The Little Friend (2002), runs to 770-plus pages. Had she wanted to write something in the spirit of the Fabritius she might have opted for a novella, in the manner, say, of Dr Jekyll and Mr Hyde or The Turn of the Screw.

Instead, she has gone to the other extreme, producing a book that rolls on and on like the Mississippi, at times sluggishly, at others torrentially, but never still. That it is too long is barely worth remarking; Tartt's two previous novels were hardly spare. The same, of course, could be said of Dickens, whose spirit haunts The Goldfinch as Marley's ghost does Ebenezer Scrooge. Another of the multitude of shades much in evidence is that of Dostoevsky: not for nothing does Tartt have a narrator called Theo, the anglicisation of Fyodor, and a chapter titled The Idiot.

For this reader, however, the presence of John Irving - another ardent Dickensian - also seemed close at hand. Like Irving, Tartt loves to immerse herself in the byways of life, be it - as here - the art world and the craft of the furniture restorer. That she knows a lot about such matters is apparent; that she needs to tell so much about them less so. Brevity, clearly, was not one of the subjects she studied at Bennington. Thus information is piled upon information, fact upon mind-numbing fact. And, like Irving too - and Dickens for that matter - Tartt draws into her fold those who have been orphaned and cut adrift.

The Goldfinch opens in Amsterdam where Theo Decker has been holed up in a hotel for more than a week. It is Christmas, when the lonely and desperate feel even more alone than they do normally. It is, Theo relates, his first time in the city, but he has seen next to nothing of it. Why? Because he's on the run, or so it seems. "The Herald Tribune had no news pertaining to my predicament but the story was all over the Dutch papers," he writes, "dense blocks of foreign print which hung, untantilizingly, just beyond the reach of my comprehension."

One was reminded of John le Carre's masterpiece, A Perfect Spy, in which Magnus Pym seeks refuge in a dead-end seaside town in order to tell his story before his masters catch up with him. Theo's is a voice to which it is necessary to warm if Tartt's novel is to grip. I was not entirely convinced by it or him, expert as he is in the business of trading mongrel antiques as genuine. This is at the crux of Tartt's novel, the idea that fiction is a legitimised form of lying and that art is whatever we are prepared to believe it to be. What does it matter if you sell wealthy people fakes if they're happy with what they've bought?

But this is getting ahead of ourselves. Theo's life has been splintered by the death of his mother. Like Fabritius, she died in a blast while she and 13-year-old Theo were visiting the Metropolitan Museum of Art in New York. But, in contrast to the explosion which killed the painter, that which claimed Theo's mother was the result of a deliberately planted bomb.

"People die, sure," Tartt has her conveniently say just before she's blown to smithereens. "But it's so heartbreaking and unnecessary how we lose things. From pure carelessness. Fires, wars. The Parthenon, used as a munitions storehouse. I guess that anything we manage to save from history is a miracle."

Here, then, is another well-signposted theme of The Goldfinch; the notion of art as transcending the ages and as a source of communication and connection between the dead and the living. There's no way of us knowing what will survive, or will in future come to be regarded as important or great. Of course, there is a crucial difference between a painting and a book. For while the latter can be easily and endlessly reproduced there is only one Mona Lisa or The Anatomy Lesson or, more pertinently, The Goldfinch.

For convenience sake, Tartt has relocated the last-mentioned to the Met. As all hell breaks loose Theo finds himself beside an old man whom he had spotted earlier with a young girl to whom he been magnetically drawn. In dying, the man passes Theo a ring - we're smack bang in Dan Brown territory now - and draws his attention to The Goldfinch which in the chaos he tucks under his arm before emerging dazed and confused into the Manhattan daylight.

In an instant the girl, who is called Pippa, becomes to Theo what Beatrice was for Dante, an angelic object of love. After all, he's convinced that she has saved his life by diverting his attention from his mother as she wandered off into that part of the gallery from which there was no escape. But Pippa - pace Great Expectations - is no substitute for Pip; rather she's as elusive and ethereal as Estella, the orphan raised and adopted by the jilted bride Miss Havisham. This is the kind of literary game-playing much loved by PhD slaves but which can do your head in if you're not careful.

Our primary concern, however, is with Theo and his odyssey through 21st-century America, which, apart from anything else, is a strenuous test of credibility. First, he is taken in by a rich family to whom he previously had only a tangential connection. Then he falls under the stewardship of Hobie, an honest man in a dishonest world, an artist not a businessman, who prefers to restore and rehabilitate furniture rather than sell it. One would not be surprised to learn that he'd been modelled on Little Nell's grandfather in The Old Curiosity Shop. In between, Theo's alcoholic father reappears on the scene, floozy in tow, determined to remove his "disoriented" - an oft-used abomination - son to the bright lights and encroaching desert of Las Vegas.

Such is this boy's own story and it is not without its affecting moments and shafts of humour. But they are too infrequent to compensate for the longueurs, melodramatic plotting, straining for effect and interminable conversations between Theo and chums like Boris, whose abusive father has shown him around the globe, including Scotland, and who comes up with a nickname for Theo: Harry Potter. "Where's your broomstick?" Boris asks, in his Australian-accented English, though his long-gone mother was Polish and his father is Ukranian. "Left it at Hogwarts," replies Theo.

And then, every hundred pages or so, Tartt remembers to remind us that Theo is pining for Pippa and still has in his possession The Goldfinch. But what's never clear is why he purloined it in the first place and why he has hung on to it. It is as much of a mystery as the painting itself, a copy of which is pasted opposite the novel's title page, the yellow-winged bird chained cruelly to a perch. If, say, you saw it out of doors, you'd think that the bird was real. It looks so natural, so right, framed against a plain wall, at the bottom of which is Fabritius's signature and the date, 1654, the year of his death.

Not only is it not typical of the times in which it was painted, it is unusual in Fabritius's oeuvre. It is an oddity, like Theo, who, in trying to comprehend it, comes to realize that "the only truths that matter to me are the ones I don't, and can't understand". A plethora of questions follows, most of which apply as much to Tartt's Goldfinch as they do to Fabritius's. Why this subject? Why not something more topical? Why not a seascape, a landscape, a history painting, a commissioned portrait of some important person, a low-life scene of drinkers in a tavern, a bunch of tulips, for heaven's sake, rather than this lonely captive? To which answers come there none. That's art for you.