The sale of the paperback "Washington Behind Closed Doors" is expected to be at least triple that of "The Company" earlier this year.

They are the same book. But you couldn't tell that by the covers.

"We expect sales of 'Washington Behind Closed Doors' to be triple 'The Company' - for a start," George Schneider, national direct sales manager of Pocket Books, said yesterday. "The effects of a TV-related series don't show up in sales until three or four days later."

It may not be reassuring to lovers of books, but is does show what a television tie-in can do for the sale of a book.

"The Company," the novel by John Ehrlichman that read like a roman a clef on his colleagues in the Nixon White House, sold better than 750,000 paperbacks earlier this year. Schneider expects its new title, "Washington Behind Closed Doors," which is tied to the lavishly promoted ABC-TV mini-series, could easily reach 2.5 million in sales.

"It's a little sneaky," said one Pocket Books spokesman asked about the covers of the two editions, the same book, exact page by exact page.

You have to read the small print on the cover of the TV-series edition to get the hint that "Washington Behind Closed Doors" just might be possibly be Ehrlichman's "The Company" under a new cover.

The TV series is emblazoned in big black letters above the faces of the ABC-TV stars, including Jason Robards, Robert Vaughn, and Cliff Robertson.

Ehrlichman shouldn't be too upset that he has lost his star billing on the cover. He's still getting the royalties for this new-covered edition of "The Company," Schneider said.

In Washington, Distirct News ordered 10,000 copies of the TV-titled book and had them on the streets about two weeks ago to get a jump on the television series.

Lou Fusco, manager of the book division, has another special order for 4,500 copies to be followed by another 6,000. He expects "very good" sales of around 21,000 or 22,000.

But then later this fall, when the first paperback edition of the fabulouly successful "Roots." appears, Fusco foresees a sale fo 65,000 to $75,000.