A DECADE AGO in a capsule review of an early foray by Andrew Greeley into sexology, it was suggested that the prolific priest-sociologist had advanced from having no unpublished thoughts to having no unpublished fantasies. Had we only known! Thanks to Warner Books, those fantasies, now fictionalized, have multiplied the biblical hundredfold with no end in sight.

Interestingly, not all the fantasies are sexual, despite those matching, tastelessly titillating jackets with their crimson draperies and statuesque women suggestive of bishops and bordellos. The fantasies have just as much to do with that broader range of human obsessions dear to commercial fiction: power, money, status. To that already heady mix Greeley adds large dollops of religion in its Roman Catholic form, still the most mystifying and intriguing for many Americans. Like the standard protagonists of such fiction, Greeley's heroes and heroines are handsome, successful, and perceptive, as well as sexy; they are also God-haunted and/or plagued with dark secrets. A few random quotations from the latest novel will give you the idea:

"At the edge of the pier, Hugh, tall, strong, and solidly muscled, momentarily appeared between the two women, one slender, the other voluptuous, one with short blond hair, the other with long black hair. The two women seemed to be fighting for him, one in the name of an overarching God, the other in the name of young love. . . .

"In the parking lot, Maria and her sons met the cardinal, Bishop McGuire, his red-haired, genial second-in- command, the cardinal's tall, striking sister-in-law, Senator Nora Cronin, and her husband, Roy Hurley, the handsome sports announcer. . . .

"When he awoke, lying on her bed, Hugh saw Maria standing above him, hands on her hips, golden and glowing in the late afternoon sun, wearing only her glasses and the plain gold cross at her throat.

" 'You like?'

"She was proud of herself, proud of her smooth, sleek body with its compact, flawlessly shaped breasts, trim waist, and slender haunches. From modest bride to naked countess. . . .

" 'I like very much.' He leaned back on his pillow. 'But . . .' "

Character and plot come from the same never-never land of bestsellerdom as the style. Hugh Donlon is an elder son destined by parental vow for the priesthood, a vocation he dutifully accepts and follows honorably despite his red-blooded urges to bed every attractive woman he meets. His younger brother Tim, lacking clerical constraints, wenches and cheats his way through life, while their sister Marge starts out badly but ends up marrying a fabulously wealthy and entirely lovable Irish nobleman. The mother and father of this brood, in addition to enjoying a sensational sex life, are, respectively, a distinguished painter of sensual forms and a judge who turns down a seat on the Supreme Court. In short, a typical Chicago Irish Catholic family!

Hugh's problems begin with a psychotic pastor in his first parish and are compounded when he falls for a recently liberated nun in graduate school. They marry, on the strength of a supposed pregnancy, and live miserably ever after. But Hugh does become a vastly successful trader of commodities, a master of revenge, and no mean Casanova into the bargain (a mother and daughter in one case). If this all sounds familiar, it should; the plot of Thy Brother's Wife has many of the same building blocks, just assembled differently.

The crisis comes when Tim gambles big and loses on the silver market, implicating the absent Hugh, now a much abused ambassador to a Third World despot who is craftier, crazier, and even more dangerous than a Chicago pastor. A vindictive judge sends Hugh to jail, but he is rescued by the shrewd sleuthing of Maria, the true love of his life, who was a shapely high school beauty in Hugh's seminary days and is now a gorgeous bank president. Her naval-hero husband, a military clone of Hugh, has recently been killed in Vietnam. As fate would have it, Hugh's wife and brother die in a plane crash during an illicit tryst in the Caribbean, leaving the now rehabilitated Hugh free to return to the priesthood or to marry Maria. But let me not spoil the ending.

Is there no grand design behind all this? Indeed there is, and Greeley spells it out in assorted prefaces and afterwords, as well as in publisher's handouts. This novel along with the previous two make up a "Passover trilogy" in which the true nature of God and the role of religion are worked out in modern parables. Man's needless crucifixion of himself and God's unfailing forgiveness are at the center of this one, which concludes on Good Friday. Sexual love as a sacrament of God's love, and the woman's role as the privileged representative of that love are all part of the message.

The ideas are worthy ones, and they put Greeley's fiction several notches above a novel like The Thorn Birds, which may well have been his inspiration. I'd always choose Andrew Greeley's gracious Yahweh, who organizes his plane crashes and other disasters for a clearly beneficent purpose, over Colleen McCullough's vindicative Jehovah who can't seem to punish his creatures enough for their sins. But good ideas, like good intendions, do not a good novel make. What we have instead is mainline commercial fiction, as addictive as bonbons or soap operas, and equally nourishing.

Happily, you don't have to choose between Colleen McCullough and Andrew Greeley if you're interested in fictional priests and religious myth-making. George Bernanos' Diary of a Country Priest is always available and, closer to home, J. F. Powers' Morte d'Urban is now back in print. And you should also be able to locate Edwin O'Connor's The Edge of Sadness. If priests, as Greeley insists, can write about sex, it seems laymen know more than a little bit about the clerical life. And for all the heavy water Greeley has made over the parabolic character of his novels, a much more authentic sense of religious parable, with its attendant paradoxes, can be found in the unsettling stories of Flannery O'Connor.

If you're interested in Greeley's ideas without the fictional trappings, you can get them by the score in A Piece of My Mind. It's a classic example of a non-book, being in fact some hundred weekly newspaper columns from 1980 to 1982 arranged under nine headings including "Women," "Politics," "Priesthood," "Church," "Youth." No genre, with the possible exception of book reviews, is more ephemeral by its very nature. Moreover, topical grouping has the unfortunate effect of revealing redundancies happily concealed by serial publication. How many times need the reader be reminded, for instance, that Pope John Paul is "complex" or that higher-ups are constantly plotting to silence Greeley? Finally, the brief space of a column (two book pages), while ideally suited to the cut and thrust of debate, gives little scope for serious reflection.

Still, there are lots of characteristically provocative ideas tossed around, from the correlation between images of a loving God and support for pre-marital chastity among the young, to the claim that bad preaching is the American Catholic Church's number one problem. In both cases he claims clear statistical support from opinion polls. On other questions he's more intuitive but probably no less right, for example in his remarks on the need to refurbish our religious symbols, especially our images of Mary.

In the end, however, form triumphs over content, and the serious reader would be well advised to look up earlier Greeley books like The New Agenda, The Jesus Myth, or The Sinai Myth for exciting tours of recent religious thought or the more scholarly The American Catholic: A Social Portrait bfor sociological analysis. The current pair of books will not be how Greeley is remembered in 20 years, or should want to be. But amid the several score of his others there are enough sturdy monuments of varying sizes and shapes for several Andrew Greeleys.