SINCE the Buildings of Ireland book series was launched in 1979, they have become the 'goto' guides for anyone interested in historical architecture throughout Ireland.
It follows the template established by Sir Nikolaus Pevsner's Buildings of England series in the 1950s, a 46-volume county-by-county guide to England's architecture.
Pevsner envisaged his Architectural Guides as portable sources of information which could be kept in car glove boxes or traveller's shoulder bags for easy reference.
The modern books offer more detailed descriptions of interesting buildings of all kinds from every period of history; castles, mansions, cathedrals, churches, public buildings, houses and 'unusual' structures of note are all covered.
Readers are provided with background information on the regions, covering major architectural themes and providing historical context to the highlights of the streets and towns under scrutiny.
A useful pictorial glossary of architectural features enables novices who might not know their skew gables from their open pediments to learn more about the detail and design of each building.
South Ulster is the fourth volume of the Buildings of Ireland series, the first to be tackled by Kells-born architectural historian and author Kevin V Mulligan, a graduate of the National University of Ireland and Trinity College Dublin.
The book continues the work begun by Alistair Rowan's painstakingly compiled guides to the buildings of Dublin, north Leinster and north-west Ulster.
"I was invited to 'express an interest' back in 2005, recalls Mulligan on how he came to be involved in the ambitious Buildings of Ireland project.
"That would have been because of my background as an architectural historian.
"I've done survey work with the National Inventory of Architectural Heritage and published various articles and books on different building types, so I suppose in that sense I was considered to be qualified for the job.
"Hopefully, the book gives a good reflection of the three counties and the diversity of buildings there."
Having been allowed to select which areas of Ireland to tackle, the Co Meath man's work in Co Monaghan turned out to have unexpected importance for the Mulligan family.
"I chose those three counties partly because my father's family are from Cavan," explains Mulligan. "Also, it wasn't too distant from where I was living at the time - though I've since moved to Co Monaghan.
Working on the book was one of the reasons we decided to relocate here. I found the countryside deeply attractive."
Picturesque though it may be, the frequently turbulent history of the south Ulster region provided an added challenge to the father of three's already imposing task.
"Destruction is more prevalent than construction and endurance," admits Mulligan.
"I tried to balance a good representation of what has survived with a good sense of what was there if there were only portions of the buildings or remnants left."
The author began his fieldwork by dividing each county into blocs before striking out from his Co Meath base to a chosen sector to take notes and photographs.
Starting in Cavan town in 2005, he then moved on to cover Monaghan and Armagh before returning to finish off Co Cavan in 2011.
"It was very methodical," explains Mulligan, "although in some cases access wasn't possible at the time and I'd then have to go back at a later date.
"Generally, people were quite interested in what I was doing but sometimes there were reservations, perhaps over fears that the building would then become listed.
"Thankfully, that fear of preservation is part of the culture that seems to be changing now."
There was also at least one instance of a local character pulling a fast one on the unsuspecting architectural historian.
Mulligan remembers: "I was driving down the road and there was a man standing there, almost as if he was expecting me.
"It was very surreal. He said to me 'so, you want to see the church?' It was as if someone at an earlier building I'd been to had tipped him off."
This Co Monaghan chancer explained he would grant the author access in exchange for being driven into town and bought a bottle of whiskey.
"So I did," Mulligan continues. "Of course, when we got back to the church I found that it was already open - as apparently it always is."
When asked about hidden architectural gems from the book, the author is quick to select Bessmount in Tyholland, Co Monaghan, a "large and vigorously modelled house" in Ruskinian Gothic, originally built in 1807.
"It's the building on the cover," enthuses Mulligan.
"That's a house very few people would know anything about as it's hidden away.
"It's intriguing because it began as a very typical late Georgian 'box' before being transformed in the later 19th century. It would be one of the special ones.
"Fellows Hall in Killylea is also a deeply intriguing house. It looks like an Italianate Victorian house but has at least three phases, with its origins in the 17th century.
"It was burnt and then rebuilt in the 1750s. The 18th century features are obvious inside and then it was enlarged again in Victorian times. It's an extraordinary house."
Though his South Ulster guide has only just been published, Mulligan is already hard at work on a new book detailing the architectural history of one of Ireland's most noted stately homes, Russborough House in Co Wicklow.
However, the Buildings of Ireland series might yet beckon the author back into the field.
"My wife's family are from Antrim and I have good knowledge of the area," he admits. "But that would be a somewhat more ambitious book.
"Antrim is a big county and Belfast is a city that would probably require its own volume in the way that Dublin has."
On the evidence of the detailed and highly accessible South Ulster volume, there can really only be one man for the job(s).
? The Buildings of Ireland, South Ulster: Armagh, Cavan and Monaghan is out now, published by Yale University Press.