These 450 pages of Q&A are less an interrogation, more a gentlemanly picking of brains. O'Driscoll, a fellow Irish poet, posed questions from the philosophical ("What has poetry taught you?") to the prosaic ("Where was the flax-dam positioned in relation to the family house?"); Heaney replied, we're told, in writing, selectively and in an order of his choosing. That said, his responses don't suggest conceit; now 70, Heaney comes across as generous, as eloquent as ever, deeply thoughtful and proud yet faintly embarrassed by his deification. As the art of poetry takes precedence over biography, more thorough quoting from Heaney's verse would have been nice.

Here, in effect, is Seamus Heaney's autobiography - and what a good way of doing it, in 500 pages of conversational interview with Dennis O'Driscoll, himself an accomplished and indeed knowledgeable poet. He compiled the highly amusing Bloodaxe Book of Poetry Quotations, which included the Irish Farmers' Journal headline noting Heaney's Nobel prize: "Bellaghy celebrates as farmer's son wins top literary award".

Which isn't to make fun of the Irish Farmers' Journal: Heaney has always been rural, making much of his rustic upbringing, and I was completely charmed by his take on his move to County Wicklow in 1972: "Horace says: vivitur parvo bene. You can live well on a little . . . [I and his wife] had both grown up in the country, so for us there was something rich and unstrange about bathing the kids by firelight, having them play around in the farmyard next door, giving them an experience of the dark country nights. It was more than nostalgic. It seemed right to supply them with memories of hedgebacks and hayfields and an open fire." Of course, for a countryman he does get about an awful lot, whether picking up the Nobel, hobnobbing with the Clintons (Bill, apparently, is as good a reader as any academic), or having his toes trodden on by squirts like me at Poetry Society events (this is true: I did tread on his toes, and he was very nice about it). He has coped with his fame, and the demands of the book-launch and dinner-party circuit, with more dignity than just about anyone you can think of - only the more rabid Ulster Unionists get really upset by him ("you could hardly quarrel with that," says Heaney, quoting one vitriolic attack).

But you can wonder what all this has to do with poetry, and sometimes I find myself sympathising with Al Alvarez's condescending assessment of his work: "It challenges no presuppositions, does not upset or scare, is mellifluous, craftsmanly, and often perfect within its chosen limits." I must confess that I picked this book up more from a sense of duty than excited curiosity - I am not deaf to the virtues of Heaney's verse, but let's just say his Collected Poems would not be the volume I would rescue from a burning library, were I allowed only one.

So if I, who am not his number one fan, can love this book, then I can only imagine what transports the true Heaneyphile will be in. O'Driscoll's questions are very well chosen: as I said, he is knowledgeable, not just about poetry, but about the world, Heaney's influences, literary, historical and political; he has a knack for drawing his subject out without ever being banal or toadying.

And as for Heaney himself . . . well, no one of any account has a bad word to say of him and, after the publication of this, that position remains unchanged. There is an easy but firm intelligence behind everything Heaney says here: it might read as comfily as a fireside chat, but everything has been considered. See how deftly he parries The Problem With Larkin. Larkin had called him "the Gombeen Man" in his letters (Ted Hughes was "the Incredible Hulk"; "not bad," says Heaney); but Heaney is both magnanimous and insightful, saying not only "I suppose I was lucky to get off as lightly as I did", but "a lot of the time in the letters, he was writing a script for himself, lines to be spoken by his inner Steptoe, the Thersites of Toad Lane". That really does look like the best way to approach the Larkin persona; and, moreover, it is a memorable phrase.

So this really is a remarkable book. There isn't a dull, vapid or useless sentence in it; it's about what it is to be human, as much as it is about what it is to be a poet (or to be Seamus Heaney). It must have taken years, and an enormous amount of energy and thought on the part of both people. Even the index is highly commendable (always a good sign that a book has had properly lavish attention spent on it). It is packed with both insight and good humour. Even those possessing only scant familiarity with Heaney's verse will like it. Unbelievably, it only costs a tenner. Off you go.

It seems extraordinary that Seamus Heaney has not been the subject of a major literary biography. Now 69, a Nobel Prize-winner, and probably the best-known living poet, he has somehow evaded biographical canonisation. The most illuminating critical reading of Heaney's work and its often deep-rooted sense of place remains Helen Vendler's Seamus Heaney, published in 1998. Now comes this big book of interviews by a fellow poet, Dennis O'Driscoll.

The late critic Ian Hamilton once described Heaney as 'the most over-interviewed of living poets', an observation with which O'Driscoll takes issue in his introduction. 'Apart from a handful of exceptions,' he writes, 'Heaney interviews, though fascinating in themselves, have been too narrow in scope to present a comprehensive portrait of the man and his times.' These 'linked interviews', as O'Driscoll calls them, set out to trace, book by book, the contours of Heaney's writing life and the events and memories that inform it. To a great degree, they succeed, though the question-and-answer format may prove a trying read for all but the faithful. It is a book, then, as O'Driscoll acknowledges, 'for readers of [Heaney's] oeuvre, on whose behalf I hope to have asked the kinds of questions which they themselves might have wished to pose'.

Interestingly, all but two of the interviews here were conducted, at Heaney's insistence, 'in writing and by post', which means the answers are often as crafted and considered as his prose but seldom attain the conversational cut-and-thrust that can occur when an interviewee sits down opposite his interrogator. A considered book, then, and perhaps in places a touch too reverent.

Its title is taken from Heaney's Nobel Prize acceptance speech, in which he described his 'journey into the wideness of language, a journey where each point of arrival - whether in one's poetry or one's life - turned out to be a stepping stone rather than a destination'. The first section, Bearings, consists of two short chapters which evoke Heaney's childhood in rural County Derry. This is familiar territory, not least because it has been mapped out in his early poems, and in the recollections gathered in his first book of essays, Preoccupations. Anahorish, Mossbawn, Lough Beg, Toome - these are the place names that, to quote Heaney on one of his formative influences, Patrick Kavanagh, are used 'as posts to fence out a personal landscape'.

His family lived in 'a one-storied, longish, lowish, thatched and whitewashed house about thirty yards in from the main road'. He remembers 'the pleasure of tearing wallpaper off the wall beside the bed' and the 'pink, distempered plaster underneath' on which he wrote. Poetry, like God, is in the details. There are recalled moments of Wordsworthian childhood wonder too: 'Out in the country on starlit nights in Glanmore, pissing at the gable of the house, I had the usual reveries of immensity.'

In his childhood, the sounds of the farm were often drowned by the roar of traffic on the road, 'backwards and forwards, morning, noon, afternoon, evening and night'. His mother, he recalls, was 'a bus-taker', and it was near the local bus stop that his younger brother, Christopher, aged three, was killed by a car. Here, Heaney recalls in spare but vivid detail the dreadful events that would later spark the poem, 'Mid-Term Break', written in one hour in 1963, while he waited for dinner in a shared student flat.

O'Driscoll deftly steers Heaney on through the key poems of his early collections, Death of a Naturalist, Door into the Dark, Wintering Out, until North, published in 1975, when their talk inevitably turns to the critical 'hammering' it received in Northern Ireland, mainly from his fellow poets there. 'I've been overwritten with praise,' says Heaney, 'and to a lesser extent with blame.' Most of that blame, for a time, centred on his supposed reluctance to meet the Troubles head-on in his poems. In North, his now famous poem, 'Whatever You Say, Say Nothing', grapples with the weight of that expectation.

In Field Work, though, published four years later, there are several poems born out of the Troubles. 'The Strand at Lough Beg' is an elegy for his second cousin, Colum McCartney, the victim of a loyalist killing gang, while 'After a Killing' alludes to the IRA's assassination of Christopher Ewart-Biggs, the British ambassador in Dublin, an act that Heaney describes as 'more like the breaking of an ancient taboo than a breach of international protocol'.

There is a telling moment here in which Heaney, at O'Driscoll's prompting, recalls the people he knew who died in the Troubles, including several Protestant and Catholic neighbours - one of whom was the IRA hunger striker Francis Hughes - as well as friends from his student days and 'one or two, at least, of the kids I'd taught in ... Ballymurphy'. What Heaney did not do, of course, was take sides, either as a poet, or, as his fame increased, a reluctant statesman.

As the book proceeds, it inevitably becomes more about Heaney's writing than his life, which takes him from Wicklow to Harvard and beyond. There are some great anecdotes about the moment, while holidaying on a Greek island, when he found out he had won the Nobel Prize for Literature and, overnight, became 'Famous Seamus'. That honour, too, brought forth the begrudgers, most notably the ever truculent journalist Eamon Dunphy, who sneered at Heaney in the Irish Independent. Dunphy is dismissed in a few lines here - 'Even at the time, I realised he was unwittingly doing me a service. He queered the pitch for stealthier people capable of more informed criticism.' Touché!

Throughout Stepping Stones there are moments when Heaney seems to belong to another era, one on which popular culture has not impinged. When asked about the 'pop poetry of the Sixties', he says: 'It was more like background music or fairground music - I enjoyed the sound of it going on around me but didn't regard it as having anything to do with the word-work.' What he calls 'the Orphic thing in Dylan' did not impress him either. You have to look to the poetry of his friend, the more mischievous Paul Muldoon, to sense the force of Dylan, and rock in general, on the contemporary poetic imagination (though Heaney does like Eminem - see p24).

The book concludes with a chapter on Heaney's recent brush with mortality in the form of the stroke he suffered in August 2006. It has made him, he says, 'more successful at staying clear'. You sense always the private, self-absorbed poet behind the public persona. O'Driscoll asks him: 'What has poetry taught you?' The answer is typically thought-through and characteristically thorough: 'That there's such a thing as truth and it can be told - slant; that subjectivity is not to be theorised away and is worth defending; that poetry itself has virtue, in the first sense of possessing a quality of moral excellence and in the sense also of possessing inherent strength of reason by its sheer made-upness, its integratis, consonatia and claritas.' Now, there's man who, as they say at home, know his onions.

Nonce Words
by Seamus Heaney
from District and Circle (2006)

The road taken
to bypass Cavan
took me west,
(a sign mistaken)
so at Derrylin
I turned east.

Sun on ice,
white floss
on reed and bush,
the bridge-iron cast
in an Advent silence
I drove across,

then pulled in,
parked, and sat
breathing mist
on the windscreen.
Requiescat ...
I got out

well happed up,
stood at the frozen
shore gazing
at rimed horizon,
my first stop
like this in years.

And blessed myself
in the name of the nonce
and happenstance,
the Who knows
and What nexts
and So be its.

Faber & Faber Ltd