A federal government employe has written a paperback bestseller on government time using government faciities and government clerical help, The Washington Post has learned.

Before editors and bureau chiefs all over town deploy their investigative reporters for a full-scale assault, though, it is important to point out that Phil Schneider's literary success is all in the line of duty. The book he wrote ("compiled" may be the better term), Policy and Supporting Positions, is an official U.S. government publication, on sale now for $6 at Government Printing Office stores, where it is the hottest selling item to come along since the previous edition of P&SP came out four years ago this month.

"Bestseller? Oh, it's a bestseller all right," said George Omas of the House Post Office and Civil Service Committee, which is the official "publisher of Schneider's book. "Judging from the phone calls we're getting up here, you'd think people will kill to get their hands on that book."

If the past is any guide, some sharpie in the private sector will pick up a copy of the new book, reproduce it and start selling a commercial version in bookstores. If that happens, as it did it 1972 and 1976, it is safe to say that Schneider's magnum opus will be sold under its popular name: The Plum Book.

Schneider's book, by either title, is the quadrennial government guide that tells, not to put too fine a point on it, which high-ranking federal jobs will be up for grabs when the new administration takes over. It lists agency, title and salary for about 4,000 of these "plum" jobs. If you're a Republican with a decent resume, it is kind of a shopping list. If you're a Democrat, it tells you which of your friends is likely to be out on the street Jan. 21.

Actually, as Schneider explains in his dry, all-business way, P&SP is more than just a list of plums. It is a complete roster of all the jobs in the government that are excepted from normal Civil Service protections. There are 6,506 positions in the book, which has the size and girth of a medium-sized city's telephone book.

"There are really only about 4,000 that are clearly political," Schneider said, adding anxiously that he would not want the professors at the Naval Academy or the comptroller of the currency's bank examiners to fear that their futures, too, are on the chopping block.

Schneider, a senior executive service official whose title, deputy assistant director of the workforce information division at the Office of Personnell Management, is not listed in P&SP, is utterly blase about the rapid ascent of his week-old volume to the top of the government's bestseller list.

"It's the third one of these I've worked on," he said, noting that The Plum Book takes considerably less effort than some of the other publications his office puts out. These include the monthly "Federal Workforce Statistics" -- "that's the green book, of course," Phil said, as if everybody read it every month -- and the annual "Occupations of Federal Blue Collar Workers," which lists 2,000 jobs spread among the 1.9 million people who work for Uncle Sam.

On first reading, P&SP seems about as dry as a book can be. For page after oversized page it presents long tables listing title, current officeholder, type of appointment (presidential appointees fall into seven different personnel categories) and salary for job after job.

Once you finish looking up your personal friends and gasping at their income (about half the jobs in PS&P pay more than $50,000 anually), there would seem to be nothing left to read.

In fact, though, Schneider and his coauthor, Frank McGrory, a GS13 at Personnel Management, have turned out a book that is alternately mysterious, wonderful and poetic.

Among the mysteries: why does the U.S. ambassador to Nigeria earn $60,662.50 per year when his colleague next door in Niger gets only $50,112.50 and their colleague in nearby Sudan makes $52,750? Why do members of the Committee for Purchase from the Blind take home a per diem of $197.72 when their colleagues down the street at the Battle Monuments Commission have to settle for "w.c." (without compensation)?

The wonderful world of government titles offers myriad paths for the wandering mind to follow. The book is full of secretaries, undersecretaries and deputy under secretaries, naturally enough. But what must it feel like to be the lucky person at Health and Human Services who bears the title "special assistant to the assistant deputy undersecretary"? wThe Pentagon has a "director of net assessment," which means, of course, that there is also a "personal and confidential assistant to the director of net assessment." The poetry of the plum book is in the names. Shakespeare had his Nick Bottom, but the federal government has Tennie P. Bottomly. Ian Fleming's fictional James Bond had a confidential aide named "Miss Moneypenny"; Uncle Sam's nonfiction Department of Energy has a "confidential assistant" named Ms. Halfpenny.

If the investigative reporters still want to probe Phil Schneider's bestseller, they might turn their attention to one glaring flaw. The color "plum," Webster's says, is "blue-red in hue," but The Plum Book has a cover of brilliant orange. "Around here," Schneider says, "we might start calling it the pumpking book."