SIDNEY JOSEPH PERELMAN (he hated his first names and got rid of them by using initials) was a agreat believer "in reticence in all things," as he once said; and that is why he has always piled one thing on another until the walls cracked and laughter ensued.

Perelman was never restrained but always reticent. You might think his posthumous book, The Last Laugh , would break new ground, especially since it includes a few sketches from his proposed but incomplete autobiography.

Here, the avid Perelman reader might think, we shall get down to the nitty-gritty of life. But the sketches of Nathanael West, his brother-in-law, and of Dorothy Parker, whom he knew for years and years, are curiously impersonal and might have been written (as far as emotional intensity is concerned) by any interviewer from a newspaper who had spent an afternoon with them.

This does not mean his last book is inferior to his other work, not at all. It is more of the same. And that, in this age so prone to tedium in letters, is a gift worth having.

When Perelman died in 1979 it was known The New Yorker possessed several manuscripts of his. These are now collected in this slender volume.

As Perelman buffs well know, the title of a Perelman story gives an exceedingly slight clue to what's in it. At best, "The Frost Is on the Noggin," for example, is less than self-explanatory. This essay deals with such pressing concerns as knowing when one is being followed by a snoop, and touches on such related matters as making a deal with the sleuth, plus shoplifting in Germany and an utterly common experience of stealing a beef pie from a delicatessen and (we have done this) scaring the wits out of a thief named Eban Locnil.

Other little slices of daily (Perelman) life are fetchngly entitled "Recapture Your Rapture in One Seedy Session," "Meanness Rising from the Suds," Portrait of the Artist as a Young Cat's-Paw," none of which gives much away, and all of which might just as readily have been entitled "Parakeets I have Flown." Indeed, one of the joys sof the reader is brooking over the titles before and after reading these pieces.

His first meeting with Parker (for it is unfair to mention Perelman's friendship with her and not produce at least one goody) was a humiliating event to our hero. Perelman presumed to criticize -- to question -- some verdict of Parker's and of course (for she was a person, you know) she construed Perelman's temperate and deferential questioning as an open rape.

Up one side and down the other she crawled, exuding venom. Perelman slunk home. (Slank is archaic.) Parker realized she had been beastly and sent him a batch of roses, and they were friends for years and years. Question: roses? But that's Parker for you. She'd have liked roses, as a peace offering, and it probably never occurred to her a man might be embarrassed by them. And Perelman, in fairness to Parker's choice of roses as an apology, probably liked them fine.

The question arises, with Perelman, why people can be found who quite dislike his work, but the answer (an infant's reflection shows) is of course apparent. Many readers are drudges, like mine donkeys. You hook the story to them and off they go, with ponderous steps and slow, dragging it behind them. They do not like strange sounds, new commands, or any visitors from outer space, so of course they do not like Perelman.

He intimidates many by his vocabulary. Even literate folk will find about three words in every Perelman piece they do not know: 10, if he's into his deli or Yiddish mode. These words are invariably jewels, and Perelman is not one to settle for a single diamond when he's got a whole vaultful.

The traditional Perelman pattern holds in his last book: he commences with some gripping sentence which almost immediately bifurcates then spawns reticulations so that by the second page you cannot remember, to save your soul, what the first two paragraphs were about.

Now, many resist this. They want to go on with the original topic and see it embroidered and developed as they chew over it after supper by the fireside (or airconditioner or ceiling fan). It disconcerts them that by a series of somewhat graceless transitions Perelman proceeds from A to M to 347. He is a great one for mixed style, in which carefully heard conversation suddenly flowers into literate English then into bombast and euphyism, to say nothing of hyperbole.

It is the technic of poetry, in which deep springs not the trifling logic of the brain feed the supply, and all Perelman plots are deep-fed and deep-sprung.

He continued to the last to love a pun. Genuine admirers of good writing, without expcetion, love puns. Although persons who cannot work them properly sit disgruntled in their corners and fume about low wit.

You may wonder, when you have given due and enormous thanks for the work of Perelman, why so much of the sparkle is on the surface. That is chiefly because sparkle is a surface phenomenon, after all. One does not know of sparkling gizzards, only sparking eyes. Perelman himself once said that in London he detected great courtesy, which was only skin deep, but deep enough for him.

And yet it may be argued the Perelman wit is of the surface and not profound. The voice you hear again and again in Perelman is the voice of -- these insights tend to flash upon one at 2 in the morning, unbidden and surprisingly accurate -- Petronius.

The same abrupt shifts of style, the same marvelous ear for conversation, the same accurate observation of pretense and sham. Only, in Perelman you are not going to be moved very deeply, and in Petronius you are.

But take him for what he is. Bright, ears-up, tail-wagging, sassy, unheroic, street-smart, involuted, suspicious, sophistocated, word-struck, irreverent, and a trifle timid, perhaps, of the hurly of life's burly.

The exact sort of writer who will never last much past his own time. How clever and how prudent we have been to have lived within it.