It was painful in the old days, making the rounds at book conventions with people yelling "Get away, vulture, you're only here to pick failures." Now, suddenly, the once-lonely people who traffic in remaindered books find themselves sought after, courted, even immitated." Things have really proliferated, everybody and his brother wants to get into the act," says Fred Weitzen of Marboro Books, almost wistful. The remainder book has at last arrived.

"REMAINDERED BOOK A LITERARY BOOM" reads a large, black headline in Free Enterprise" the magazine that makes youmoney," where the business is estimated at $150 million a year. This popularity, says Washington's Bill Kramer, who deals in low-priced remainders on both a wholesale and retail level, is "an inevitable consequence of inflationary times. Book sellers are finding reluctance on the part of their customers to spend the kind of money new books cost, so they have to offer something else to buy," Adds Robert McGee, head of a remainder operation set up by the Walden chain, "The field has nowhere to go but up. Most people cannot afford $20 books."

To grasp exactly how big the remainder business has become, a trip to an industrial park in Avenel, N.J., is necessary. There, hard by companies with names like Alcan, Rockbestos and Bildisco, sits a quartermillion square foot warehouse occupied by the Outlet Book co. and its mail-order affiliate, Publisher's Central Bureau.

Inside the building's cool, white exterior are 24-foot ceilings, 300-foot aisles, hundreds of employes and huge suspended sacks of "Flo-pak" packing material looking like enormous baby bottles.

And books.

Two to four million books. "Have you evers seen so many books at one time?" asks a proud employe. "And we know where they all are, we think."

What they all are, exactly what makes books remainder (or promotional books as they are known in the industry) is a more difficult question still, but there is one key element and that is price. In three different ways, these books come cheap.

Though seeing them lumped together on a come-on sale table at a regular book store, or in stores that feature remainders almost exclusively like Kramerbooks on Connecticut Avenue or the Marboro shops tends to disguise the fact, these books come in distinct categories, all of them bargains of kins or another.

The true remainder - when most people think remainders, they think in terms of the dictionary definition, "copies of a book remaining in the publisher's stock when sales have ceased or become unprofitable." In blunter terms, reminder dealers talk of eating up publisher's mistakes, making good on the bad guesses on what the public wants, like the close to 100,000 leftover copies of Rose Kennedy's "Times to Remember."

Special import books - sometimes called "extra value books" by PR minded folks, these usually heavily illustrated volumes are not reduced from their original price like the true remainder but, as one bookman put it, "give the immediate impression of being a real bargain" because low printing costs overseas allow for a low price here.

It is these books which give rise to the jokes about remainders. Like the idea, put forward by Allan Stypeck, whose Second Story warehouse in Alexandria is home to close to half a million books, that "the ideal remainder would be 'Gestapo Cats at the Masters,' with Fritz the Cat in an SS uniform swinging a club on the cover. That would make a fortune."

Reprint - a reprint is just what it sound like, the reprinting of an already successful book but at a much lower cost. Helping to keep the price way down is a trio of factors: the initial start-up costs of the book have already been paid by the original publisher, the quantities printed are much larger than the first time, and the market is more predictable by the time reprinting is considered. Says Norman Blaustein, whose Harlem Book Co. was one of the founders of modern remaindering, "Reprints are the future of our industry."

Biggest of the reprinters is the Outlook-Publishers Central combine, which markets books under a seemingly endless list of reprint lines like Bramhall House, Weathervane, Crescent and Avenel. Sometimes reprints are of volumes long out of print - Outlook has sold 400,000 copies of a 1901 Gray's Anatomy at "Only $7.98" - and sometimes they are the offshoot of a true remainder that has gained enormous success, like Outlook's all-time best-seller, "Norman Rockwell Illustrated," which has sold a whopping 800,000 reprint copies at $7.68 each.

Though obviously popular, remainders, says Kramer's Bill Kramer, still have to live down "the popular misconception that equates them with books that nobody wants. That really isn't the case. I've always believed every book has a market at a price, and remaindering is the process of finding it."

The process starts when a publisher decides that, due to warehousing costs as much as anything else, he can no longer afford to keep around his leftover copies of last year's also ran. While something of an old-boy network tends to operate here on occasion, in general the publisher simply contacts the two dozen or so major remainder houses and asks them to bid on the entire lot of books available, whether it be 1,000 or 100,000.

"We go up to New York and look at the books before we bid," Kramer explain. "You pick up the book, heft it, say 'Hmm, I think we can get a certain price on this' and then you place your bid accordingly."

The companies bidding come in different sizes with different interests. Outlook is the giant of the industry, with 20,000 different titles in stock and a mailing list that runs into the millions. Marboro tends to see itself as dealing in more serious books, and Kramer, dealing at first in academic remainders, now mainly in the area of belles lettres , is more serious still.

"We buy books to be read, not nonbooks to be sort of browsed," explains Bill Kramer, adding puckishly, "I don't think there is much of a need for any more 'All-Color Books of Cats.'" In the same vein in his ad in a recent New york Review of Books which headlined "James Joyce, John Milton, Leo Tolstoy and Henry James axed by publishers, join other luminaries on distinguished remainder list."

A typical transaction (though probably not for Kramer) would work as follows: A company bids on 10,000 copies of Muhammad Ali's "The Greatest," offering $1.25 per copy on a book that originally cost $10. The bid is accepted, and the company proceeds to retail "The Greatest" at $2.98 per. The original publisher gets the books taken off his hands, the book buyer gets a bargain and the remainderer makes a pleasant profit.

It may all sound ridiculously easy, but cautions Marboro's Fred Weitzen, "this business is very dangerous. All you have to do is buy too many copies of a book you paid too much for and you'll be in real trouble. Evaluation is very important, and its not something you get the feel of in a few weeks. You have to know what price is going to make it salable. You bid too high, you'll be in real serious trouble, real serious trouble."

And what does "real serious trouble" mean? For a giant like Outlook, it means nothing more than reducing the price until enough people find it attractive. "The Front Page History of the World Wars," for instance, which was expected to be a big seller (see "Nazi Cats at the Olympic") did poorly at $7.98, not so much better at $3.98, until finally, according to vice-president Alan Mirken, "It just ran away at $1 a copy. Sooner or later, there's always something you can do with it."

For a smaller company like Kramer, owner Bill Kramer takes a deep breath and says "If I make a wrong guess as a wholesaler I eat it. I can try and find another buyer, or I throw them away. I hate to do it, but it sometimes happens. Even if I wanted to pulp a book, it would cost me a nickel a copy."

Equally disturbed, if not more so, was Marboro's Weitzen, who responded with a "How could you even think such a thing?" when asked about remainders that remain unsold. "We might well assortments of books to go at 49 cents and 59 cents each to chain stores, and you've got every kind of charity and prison asking for books.

"Throwing out? Never. That would hurt me."