ARCHAEOLOGY IS a universal subject, like education, literature, the theater and the concert stage, in which everyone feels himself quite competent, actually, to give advice.

Around one of the garden pools of Pompeii small holes were found, undoubtedly for posts, and the author of this splendid book, Wilhelmina F. Jashemski, suggests that these posts were for vines that (she goes on) doubtless formed a green and living roof for the pool.

Surely not. They held vines most likely, but the gardener would have grown them in swags or garlands from post to post, not on cross-pieces over the pool. The pool (as in the dozens of other examples at Pompeii) would have been completely open to the sunlight.

Of course I have never been to Pompeii. No need to, not with the Jashemski book at hand. Now we can sit at our fireside and learn far more of Pompeiian gardens than we could learn on the site, and without the twin dangers of eruptive Vesuvius or disruptive strikes.

The book falls into that category of priceless works that represent the thought and the researches of a lifetime. There is more information in Jashemski's notes (in the back of the volume) than in many another garden book's text with photographs chosen from the 30,000 color pictures (and even more black and white ones) taken by the author's husband, Stanley A. Jashemski, a physicist who used to take unpaid leave from his lab to accompany his wife to Pompeii almost every summer.

When she began visiting Pompeii in the mid-'50s, the author wrongly assumed that these famous gardens, covered with 15 feet of volcanic lapilli in 79 A.D. and greatly excavated in the 19th century, had been exhaustively studied. She supposed one little trip to see them would provide plenty of information for her book. It was far, far otherwise.

Garden after garden, it turned out, had been summarily laid bare and the site gravely damaged by traffic of one kind or another, and commonly no notes had been taken by the original excavators. Sometimes the author would find a reference to "indications" that there had been trees in a garden, but no measurements of the root cavities, and not even a hint where the trees had stood. Much that might have been learned, if a Jashemski had first excavated the gardens, has now been lost forever.

Now one common, though far from universal, sort of Pompeiian garden is the peristyle garden. One enters the house through an atrium, usually with a hole in the roof so water can fall into a small pool with conduits leading to a cistern for storing water.Then, beyond, is a courtyard surrounded by columns, the peristyle.

When Jashemski began her work at Pompeii, she "searched in vain for a detailed excavation report for (even) one peristyle garden." So her excitement was great when in 1973 she undertook the excavation of a large peristyle garden, the first to be discovered for almost 20 years and the only one, of course, totally untouched by earlier tamperers.

Since not everybody is automatically fascinated by Pompeiian gardens, to begin with, some points should be made. These gardens, some no larger than a little light well, while others were like those of Georgetown -- from the size of a living room on up -- were closely bound to Pompeiian life. Some of them had commercial uses: there were vineyards and nurseries, and some were the setting for small restaurants. In some of them wool was processed; in most of them food was raised. Often religious activities, from animal sacrifices to meditation, were carried out in the garden.

The gardens moreover give new and sound ideas of the quality of ancient urban life. We have all been assuming Pompeii was a congested narrow-streeted provincial town with dirty pictures on the walls and that's about it.

On the contrary, Jashemski shows that a third of the area of Pompeii was open space. She has tabulated the percentage of land given to gardens (5.4 percent are in gardens attached to houses, while large food gardens account for 9.7 percent, and gardens connected to public buildings occupy another 2.6 percent).

It is only through such specific information that one can at last get an idea of the daily life. We now know, for example, that most of the dwellings were single-family row houses with a garden, however tiny. Even people without gardens were only a matter of minutes, by foot, from green spaces. Jashemski makes Pompeii sound rather a paradise.

We also had assumed these small courtyard gardens were planted as we would plant them nowadays and are even more astonished than Jashemski was to learn that small town gardens had enormous fig, olive and cherry trees. Often the planting was informal, not to say haphazard.

Thanks to relatively new techniques, concrete casts can be made of root cavities, and since the root patterns of a fig, say, differ from those of an olive, it is possible to say with certainty what some of the plants were that were flourishing the day the volcano erupted.

If the site has not been too severely disturbed, it is possible to find pollen from plants still, and this can be identified in laboratories. Thus we now know that although the olive is an uncommon tree in Pompeii today, it was frequent in classical times there.

The text, quite apart from the superb pictures (hardly a page fails to have at least one informative illustration), is not only readable but terse and exciting, in the manner of books based on enormous numbers of facts, tempered with many years of digesting them.

It speaks well for the author's warmth and enthusiasm that a number of laborers who began as mere warm bodies to help in the heavy physical work, have themselves become specialists; and the obvious respect and affection that the author often feels towards those who sweated much in this archaeological work is quite touching.

Often she would be puzzled at some land contour, or some hole that did not seem understandable, and time and again a laborer would show her a living analogy on a farm near Pompeii. Once a truck driver's father-in-law was able to answer a puzzling question about a Pompeiian vineyard via (pathway) by showing Jashemski a via in his own modern vineyard.

Surprisingly often there were paintings on garden walls, and these are given much attention in the book. They are not, by the way, pornographic.

Or consider the matter of garden pools. Jashemski not only illustrates them lavishly, but gives their measurements. Some are only a yard square and three inches deep. Others are more than six feet deep and the size of a swimming pool. Some have fountains -- Jashemski goes into great detail on exactly what kinds of fountains. There is information on the town water supply, and pictures of the curious brick water towers, from which water was distributed to townsmen and their gardens.

One does not expect, when he picks up the book, to be so soon involved in urban planning, in the wool and fishsauce business (important local industries) or the nature of family altars. But Jashemski quickly saw that these old gardens were intimately connected with life at all levels. Her information is massive, her eye for detail is telling, and her eminent good sense and modesty are all-pervading. Hers is an extraordinary book, which may well have astonished her publishers who, to do them credit, have exerted themselves vastly to produce a book that is not less than stunning. Both the National Endowment for the Humanities and the University of Maryland's general research board gave money towards this book, and doubtless new congratulate themselves on a buck well spent.