THE LAST TIME Erich Segal '58 got the urge to write at length about his alma mater, he produced Love Story, and Freshman Week hasn't been the same since.

Fifteen years later, it seems our favorite Yale professor of classics is out to change the face of fair Harvard's reunions as well. Try as he might, though, Segal just won't be accomplishing it with The Class, a fictional account of the exploits of his own class before and after June 12, 1958.

What he has accomplished is the production of 592 pages that read like an explication of a "Class Notes" section in Harvard Magazine--fascinating but not penetrating. What he hasn't done--and it's this that makes The Class so contrived--is allow for the possibility that one or two of his classmates enjoy what they do or are Heaven forbid, happily married.

This is not to say that Harvard affiliates and non-affiliates alike won't eat it up--its publication date is today and it's already climbing the bestseller lists--or that it has no redeeming value. Segal does more with his stereotypes than, say, Alice Adams '46, whose Superior Women, a tale of Radcliffe in the '40s and the havoc it wreaked later, all but announced its conclusion halfway through. There are a few surprises.

Coming from the man who, in Love Story, captured the Harvard of the early '60s right down to 'Cliffie bitchiness and the secular religion that is Crimson hockey, it's no surprise that the college portions of the novel ring true. The one problem here is that the period 1954-58 was not, to put it mildly, a time of campus unrest or even great social shakeups. Segal makes up for this with painstaking accounts of such bygone rigors as the Step Test and the Swim Test, while ignoring real campus news like the hockey heyday of Bob (really '58) and Bill ('56) Cleary (who did make it into Love Story).

But believable accounts of "life after college" in the novel-of-Harvard genre--chief among them Anton Myrer '44s. The Last Convertible--are almost absent from the late sections of Segal's magnum opus. As far a comparisons go, let it be said that Rona Jaffe '51 has a lock on the 25th Reunion trash novel category of this ilk, and Class Reunion wasn't anywhere near as pretentious as The Class, Even Love Story, while making no attempts at profundity (except, of course, in its one infamous and unfortunate definition of love), has its place in this venerable category of literature. Maybe Segal is just trying too hard.

EVEN BEFORE page one, the Harvard-centric nature of The Class is apparent, as Segal quotes William James on the joy of being a "son of Harvard," and notes that James received his M.D. (Harvard, of course) in 1869. Later, he also cites John Updike '54, Ralph Waldo Emerson '21 (1821, that is), e.e. cummings '15, ad nauseum. Most irritating, though, is his choice of members of the Class of 1958.

This is Harvard Diversity. Meet:

* Danny Rossi, The Musical Genius Who Sacrifices Everything To Go To Harvard;

* George Keller, The Eastern European Refugee Who Sacrifices Everything To Go To America;

* Theodore Lambros, The Townie Who Grew Up In The Shadow Of The Yard But Loves Harvard Anyway:

* Jason Gilbert, The Great Athlete Who's Ashamed Of Being Jewish;

* (And, lest we forget Oliver Barrett IV '64) Andrew Eliot, The Preppy With The Heart Of Gold.

A couple of these fictitious sons of Harvard--the token preppie's last name has necessitated a disclaimer in the "Publisher's Note" actually take less than, predictable paths, but not before a detour through a detail and cliche-loaded section about 1954-58. The details are sure to cause reminiscing in Harvard Clubs nationwide, if not in dorm rooms:

After the official registration, they had to run an endless gauntlet of wild, paper-waving proselytizers, all vociferously urging Harvard's now-official freshmen to join the Young Democrats, Republicans, Liberals, Conservatives mountain climbers, scuba divers, and so on...

What was that gray sliced stuff slapped at them at the first station? The serving biddies claimed it was meat. It looked like innersoles to most and tasted much that way to all. It was no consolation that they could eat all they wanted. For who would ever want more of this unchewable enigma?

THE CLICHES are far less interesting. The Preppie-Townie Couple Who Make Love Whenever They Can, The Cliffie Who Won't Go All The Way. The Suicides Under Academic Pressure--all awash in a sea of sentence fragments--make you wonder how anybody even makes it to the 25th Reunion. Under the truisms, however, In a number of truths surprisingly enough, and once Segal is free of the burden of relating everything to The Harvard Experience, these begin to appear.

By far the most interesting member of The Class (as Segal and diarist Andrew Eliot, the sometime narrator insist upon calling it) is Theodore Lambros, the commuter who aspires to be a Harvard classics professor. Ted pays his way by working at his father's restaurant, picking up a preppy wife along the way, and then plunges into the rat race that is the tenure track. As a classicist who taught at Harvard and Princeton before winding up at Yale, Segal knows the intimate details of the hard-fought battles that surround lifetime appointments including the much-desired favorable reviews in the Confy (sic) Guide, which Ted purchases at 6 a.m. so nobody will see him.

First he glanced left and right to make sure the coast was clear. Then be casually picked up a New York times and swittly snatched a copy of The Harvard Crimson Confidential Guide to Student Courses immediately burying it in the paper. Having carried the exact change in his hand he quickly paid and was off.

Unable to bear the tension of the journey home, he hastened around the kiosk into one of the telephone booths. He pulled out the magazine his fingers nervously groping for the classics evaluations.

First he looked at Greek A. It was an auspicious start "Dr. Lambros is a marvelous guide through the intricacies of this difficult language. He makes what could be a boring task an absolute delight."

Then Latin 2A "Students taking this course will be well advised to opt for Dr. Lambros's section. He is arguably the liveliest teacher in the department.

He closed the book, shoved it back into the Times, and let out an inner whoop of joy.

The whoop gets larger when John Finley 25. Master of Eliot House and Eliot Professor of Greek congratulates him moments later on his marvelous reviews.

Pleasantly idiosyncratic interludes like this one are far too few, however, and the only character whose plot line is nearly as interesting as Ted's is Jason's. Child of assimilation-bent parents, he doesn't come to terms with his Jewish ancestry until he's nearly through law school (Harvard, of course). His life in Israel doemonstrates that not only is there life after Harvard, there's life after Harvard Law--but remember, this is fiction.

THE OTHER THREE characters behave more predictably that even Segal probably would like, with melodrama dominating. Danny's life much the way respectability comes to define. Andrew's George the made Hungarian, "applies his passion for power and government to his studies which--almost inevitably, it seems--wind up under the auspices of Henry Kissinger 50 People take drugs, marriages crumble children rebel, in these lives must the way they do in non Harvard ones it's just that here they all have class years after their names.

Perhaps it's this quality more than any other that will make The Class such a hit in and out of Cambridge regardless of its often fantastical plots and awkward writing. Andrew Eliot writes in his diary about a classmate. I guess he just didn't know how to be happy. He adds--surely to the delight of any number of readers who knew it was coming--That thing the Harvard Boola boola.