Journalists, famously, never agree on anything, least of all the merit of other journalists. But there was a consensus last year when John Jeremiah Sullivan dropped a collection of his essays, Pulphead. The reviews ranged from effusive to hysterical in their praise. Sullivan, a 38-year-old who lives in North Carolina, was commended for his keen eye, offbeat sensibilities and the ease with which he meshed memoir and dense reporting. He was unanimously accepted as a new generation's Tom Wolfe.

Sullivan's British publisher, Random House, clearly took note and has now released his first book, Blood Horses: Notes of a Sportswriter's Son, which came out in the States in 2004. It takes just one subject, rather than the disparate, scarcely linked stories of Pulphead, but all of the elegance and craft he displayed in the later book are present once again. In fact, the extra scope Sullivan is afforded by the full-length Blood Horses might just make it a more satisfying and enduring read.

Writing a successful book about horses is no easy feat, as Sullivan points out on a couple of occasions. "Beasts do not make good protagonists," he notes early on, "for the simple reason that unless you are younger than 10 or have money riding on their success or failure, it is hard to identify with them fully." Sullivan follows the example of others and weaves in stories of "human beings whose fates run more or less parallel to the track". In his case, it is most prominently his father, Mike Sullivan, a sports writer who drank, smoked and junk-fed himself to death at the age of 54.

Blood Horses also details the journey of thoroughbreds from the Middle East to the west. But the book really sparkles when Sullivan reminisces on his father and his own experiences as a sports-indifferent child, dragged around the stadia and racecourses of the American south. Mike is the kind of guy who drank Tab soda because "no one ever asks you for a sip", and whose militant digestion once led him to propose a book called "Diarrhoea: An Autobiography". Mostly, though, he is a writer who, despite obvious gifts, never realised his potential. Two books in, this is evidently a fate not likely to befall his son.

A couple of years ago John Jeremiah Sullivan published Pulphead, a collection of eloquent and extremely entertaining essays on such subjects as Christian rock festivals, reality TV, the ageing rocker Axl Rose, the Tea Party movement, and the cave paintings of the "Southern Death Cult" (the ceremonial remains of the Mississippian culture that dominated south-eastern America until around 1500). Pulphead became a New York Times bestseller, and established Sullivan as an outstanding proponent of long-form journalism  the great American tradition of Tom Wolfe, Joan Didion, Norman Mailer and latterly, David Foster Wallace. Long-form journalism, done well, is qualitatively different from any form of reportage that we regularly see in this country  in the space given to it, in the depth of research undertaken, and most of all, in its ambitions. It embodies the ideal that journalism should be as carefully shaped and well-written as fiction.

The habit of taking "low" subjects seriously comes with the territory  Sullivan lavishes FR Leavis-style levels of attention on Axl Rose's "snaky side-footed dance", and is very good at explaining the mechanics of pop music. But whereas there's usually some archness or condescension involved in this, Sullivan's signature style is enthusiastic and empathetic. He is a master of the autobiographical switchback. At a Christian rock festival, where the reader is expecting satirical disdain, Sullivan bonds unexpectedly with "a bunch of West Virginia guys on fire for Christ", and then describes his own teenage "Jesus phase".

His writing has a lovely looseness about it: he can zoom up and down the registers, from high art to the vernacular, but without making a conspicuous display of his agility. Rather, he shapes his style and approach to the material, switching as necessary between reportage, essayistic meditation and personal reminiscence. He also has a sharp comic turn of phrase. Richard Branson is "that weird and whispery mogul-faun, Sir Richard". Concerning reality TV, he concludes: "This is us, a people of savage sentimentality, weeping and lifting weights."

Blood Horses: Notes of a Sportswriter's Son is Sullivan's first book. It was initially published in 2004 and is now printed for the first time in the UK in the wake of Pulphead's success. It shows him working on the techniques that he would later perfect; it's a good, funny, moving book, not as assured as his later essays, but consistently interesting nevertheless. Sullivan's father Mike was a sportswriter for the Courier-Journal, a Kentucky newspaper, who in his time covered Muhammad Ali, the young John McEnroe and Michael Jordan in his college days, along with many no-doubt classic sporting episodes less immediately meaningful to a British reader (for example, the Cleveland Indians during their late-90s streak). He was also a man who, as they say, "did not take care of himself". He chain-smoked, ate too much and "drank a lot, rarely ordering beer except by the pitcher and keeping an oft-replaced bottle of whiskey on the top of the fridge". Two months before his father's early death, Sullivan Jr asked him what he remembered best from his decades in the press box. He replied: "I was at Secretariat's Derby, in 73. That was  just beauty, you know?"

Sullivan didn't really know: he was never a sports fan, and had managed to ignore the Derby, though he grew up just over the river from its venue in Louisville. So he wrote this book, partly a tribute to his father, partly an attempt to tell the story of Secretariat, who won not just the Derby but also the other two great races of the Triple Crown in record time, and partly a study of horse racing and horses in general. So there are autobiographical sections; historical descriptions of Kentucky; colour passages about trips to the Derby and horse-race sales; and brief accounts of the evolution and history of equus ferus caballus.

If, like me, you're interested in horse racing in principle but know nothing about it, then Blood Horses provides a stimulating, if not exactly rounded, introduction. I was aware of the term "thoroughbred", for example, but had only a vague idea what it meant. All thoroughbreds are supposedly descended from three "foundation sires"  18th century horses, which were themselves the product of three fabled stallions imported from the Middle East and crossbred with English mares  the Byerley Turk, the Darley Arabian, and the Godolphin Arabian. All genealogies are recorded in the Stud Book, first compiled in 1791, 35 years before Burke's Peerage. Thoroughbreds are one vast, high-achieving, inbred family. One expert that Sullivan speaks to says that today they have on average "a 16% genetic relatedness  somewhere between first cousins and brother or sister". In Kentucky, racehorses are exercised for just one or two hours every day; the rest of their lives are spent in the stalls. Each horse costs millions to buy and millions to maintain. The prospect of them hurting themselves while unsupervised in a field is too dangerous to contemplate. Each horse, according to the Kentucky trainer John T Ward, is given "his own individual educational programme  it's like Montessori". "The trick," he explains, "is you can't demoralise their minds. They remember everything."

Sullivan's portrait of his father is probably the best aspect of the book. Mike Sullivan was, to put it harshly, a failed writer. The son of an Irish construction worker whose early death left him devastated, he dropped out of college in the late 1960s and lived in a wild-sounding collective in Memphis, about which Sullivan is able to discover practically nothing. Eventually, demoralised by reading Joyce, he gave up his artistic ambitions and became a sportswriter, turning in eccentric articles that were "dense and allusive and saddled, at times, with what could be called pedantic humour". The sense of failure, it seems, entered his soul. Though loving and funny, he was also angry, depressed and self-destructive. Sullivan is aware that his own life has been moulded by his father's passions and frustrations. "Sons," he writes, "often wander like sleepwalkers into their fathers' defeats."

The weakness of Blood Horses is that the separate strands do not really cohere. Sullivan incorporates a lot of miscellaneous horse material  about the role of horses in Cortes's defeat of the Aztecs, for instance, or Kaspar Hauser's love of riding  which is fascinating, but random. As he points out, the histories of humans and horses are intimately intertwined; once you start collecting horse-related arcana, it is hard to know where to stop. But it is clear that Cortes and Hauser don't have much to do with Mike Sullivan; indeed, it turns out that his father was generally a baseball man.

The book also showcases Sullivan Jr's one weakness as a writer  a slight tendency to glib hyperbole. When Secretariat won the Belmont Stakes, he got so far ahead that the cameraman didn't know what to do and left the screen empty for seven seconds. "In the history of profound absences  the gaps in Sappho's fragments, Christ's tomb, the black panels of Rothko's chapel  this is among the most beautiful," gasps Sullivan.

In general, though, he is unfailingly good company, always curious, often very funny. "And the jockeys!" he writes. "Who could not love a sport with its own paid battalion of wee men, their bright, gay silks, their young faces, their ambiguous quasi-midgetry?"