"How many! … All these here once walked round Dublin. Faithful departed. As you are now, so once were we…"

Nine-thousand-seven-hundred is how many: 9,700 men and women who once walked around Dublin, Cork, Belfast and the grass tracks in between, from the dawn of written history to the 21st century. The Royal Irish Academy's monumental Dictionary of Irish Biography, all 9,000 pages of it, has just been published to the sound of dropping jaws, purring appreciation and universal acclaim.

The nine handsome volumes can be purchased in your local bookshop for €730 or £650 (rising by around 15% at the end of January), while the searchable online version is priced at £300 for five years' access.

It represents the work of almost two decades for the core group, gathered together by the RIA after its then president, Trinity professor Aidan Clarke, gave the project impetus in the early 1990s. A part-time researcher trawled existing biographical dictionaries to establish a database, but it wasn't until the Higher Education Authority delivered a grant in 1997 that the project went into full swing.

Marshaled by its editors, UCD historian James McGuire and James Quinn of the RIA, a team was assembled and an agreement struck with Cambridge University Press (CUP), which was prepared to publish without subsidy. With a staff of 24 at its peak, and dozens more coming and going over the years, the task of deciding who merited a biography, and who should write it, was an onerous responsibility.

There are always going to be contested omissions from such a list, and everyone will have an opinion. So, is McGuire confident that it has a biography of everyone it should have?

"No," he says. "Confidence of that sort would come close to complacency."

Everyone will play the 'who-should-be-in' game, although it will be hard to come up with very many. The editors have used as a guiding principle those who were "most likely to be objects of enquiry in the 21st century", which few can argue with.

One man who it is disappointing to see omitted is HWD Dunlop. He was the man who almost single-handedly conceived of and built the stadium at Lansdowne Road, as well as laying important foundation stones for Irish athletics and rugby.

Another eminent Victorian the editors might consider next time is an all-rounder who typified that age: Douglas Ogilby from Donemana, Co Tyrone, was a four-time Irish sprint champion and delegate at the meeting that founded the IRFU. On graduating from Trinity, he headed for Australia where he became a leading naturalist. He was sacked by the Sydney museum for "extreme and undiscriminating affinity for alcohol", but was still sober enough during a long career to identify and name 154 new species of fish.

While the series celebrates the great and good, there are plenty of others who were neither. Try Bishop John Atherton of Lismore, hanged for buggery, or Martin 'the General' Cahill. There is a heavy representation of those who fought in the years from 1916 to 1923, while sportsmen also feature ­heavily.

One delightful feature of the Dictionary is that the touch is lightened when required; there are plenty of delicious lines to brighten the dry details of a CV. Theatrical comic Jimmy O'Dea's father took the advice offered to Mrs Worthington, telling Jimmy "he'd sooner see him in a coffin than on the stage". And former tánaiste John Wilson pens a tribute to his old Cavan football teammate John Joe O'Reilly, telling movingly of how he heard of his untimely death.

Wilson is one of more than 600 external contributors, including novelist Colm Tóibín, who provides a measured assessment of Francis Stuart, and Bruce Bradley, who profiles James Joyce.

The nine volumes ignore the living, and those who died after 2002 (art writer Dorothy Walker, who died in December that year, was the most recent to be selected), which means we will have to wait for the next edition to read the verdict on Charles Haughey. The project is working on the first
of twice-yearly supplements to be published online, starting in May. These supplements will include not just those who have died since 2002, but others who may have been omitted inadvertently.

"Initially there was to be a print edition only, but in 2004 CUP persuaded the academy that there would have to be a simultaneous online version as well," McGuire explains. "It was the right decision, though it had considerable implications for the timetable as over 7,000 entries had already been written and had to be manually coded."

It may seem churlish to start picking holes, but this is a set of books with a hefty price tag and one that will sit on library shelves long after its creators have appeared in an online supplement. However, with just a few weeks to sample the text, several errors and omissions that should have been caught have become apparent.

The biography of Joseph F O'Reilly (the aide to Michael Collins who tried to get the GAA to cancel the match on 'Bloody Sunday') says it was the All-Ireland football final – it was a mere 'challenge'; pioneering film maker Kieran Hickey's brother Des was elder, not younger; Sir Timothy O'Brien, the man from Baggot Street who captained England at cricket, isn't the highest scoring Irish batsman "by some distance" (he has 7,000 runs less than Freddie Fane) and didn't play for Middlesex alongside WG Grace (who played for Gloucestershire).

There are important omissions: Sir Tim O'Brien's otherwise solid biography omits completely the scandalous slander case in which O'Brien tried to nobble the jury, and led to the financial ruin which dominated the second half of his long life. And while there is plenty to fill the biography of eccentric fizzy drinks magnate Sir Stanley Cochrane, surely a line or two could have acknowledged his role in the foundation of the scouting movement.

With the online edition always open to correction and re-evaluation, the 8.36 million words will be added to over the coming years. Similar projects in other countries add extra volumes periodically, and McGuire does not rule out a 10th volume. "At present the focus is on the online supplements, but the case for producing a print volume when critical mass has been established seems overwhelming."

There are many highlights between the collection's green board covers – Frank Callanan on Parnell to pick one. Managing editor McGuire, when pressed, particularly likes Ian d'Alton on Molly Keane and John A Murphy on John B Keane.

This is not the best timing for a wallet – and bookcase – stretching set such as this, but then it is a once-in-a-lifetime purchase.

www.dib.ie