After 182 years, the Library of Congress finally got around to compiling a guide for the 2 million visitors and half-million researchers who stream to the institution each year.

The 128-page paperback, which went on sale late last month, was officially launched yesterday at a reception in the main library's Whitehall Room.

Geared toward both serious scholars and first-time visitors, the guide combines "bits and pieces of the library's existing pamphlets and one-sheet handouts" with background on the library's 19 reading rooms and 78 million books, maps, prints, films, tapes, photographs, newspapers, magazines and manuscripts, said spokesman Craig D'Ooge.

"I'd say we've needed this road map for at least the last 100 years," said Charles Goodrum, the book's co-author. "It's the biggest library in the world, it's tough to find the book you want and everything takes longer than it normally should."

Funded by private donations and currently selling for $5.95 at the information counter in the library's Jefferson Building, the guide is an attempt to dispel the many myths about the institution and to woo a few more visitors.

"If you refer to the Vatican, people know exactly what you're talking about," said Goodrum. "That's how it should be with the library. It's not a part of the national memory."

The frustration some visiting researchers experience may stem from the many misconceptions about the library, Goodrum said. The biggest misconception? "That we have a copy of every book ever printed," he said. "That's not true, but we do have more books than any other library."

Goodrum then rattled off a series of amazing-but-true details about the library:

* Only 20 percent of the collections are books.

* Only one-fourth of that 20 percent are in English.

* The Library's oldest relic is an original Buddhist prayer Sutra, dated 770 A.D.

It took Goodrum and co-author Helen Dalrymple "three to four months" to complete the guide. But since both had worked previously in the library's planning office, "we knew a lot about the place to begin with," said Dalrymple. "It's not like we were starting from ground zero."