Rosemary Sullivan, 71, has spent a lifetime collecting books, many of them rare and first editions. For the past four decades, she's also been a notable book seller.

She intends to pare down her collection by close to 5,000 volumes in a sale that will start at 11 a.m. today conducted by the Three Rivers Auction Company of Washington, 382 West Chestnut St., Washington. The doors open at 9.

"As a child, my father and I used to go to auctions near our home in upstate New York near Albany where he bought boxes of books," said Mrs. Sullivan. "I loved to read, and got caught up in collecting at a very early age.

After she married Robert "Sully" Sullivan, she moved to Washington in 1957 and merged her then-limited collection with that of her husband, himself an inveterate book collector.

"Both Bob and I loved antiques, and after we settled in, we began attending auctions looking for furniture," said Mrs. Sullivan. "We also ended up buying collectible books."

Over the years, the Sullivans purchased books at sales in eastern Pennsylvania, West Virginia and Ohio. They also bought from catalogues, from local collectors like Gov. Edward Martin and from local historians Albert Miller (founder of the Meadowcroft Museum of Rural Life), A. D. White, Noah Thompson, Ray Knestrick and Earle Forrest.

As far as she can remember, Mrs. Sullivan said the highest price she ever paid for a single book was $3,800 for a title she doesn't want to reveal. Her main focus in book collecting lies in Americana and genealogy, while Mr. Sullivan's knowledge of gardening, jewelry making and glass is reflected in his collection.

For the past four decades, the couple sold books from their home in Washington via catalogue, at occasional shows and history seminars and, in the last 10 years, via the Internet. At one time, Mrs. Sullivan estimates they had amassed a collection of 20,000 to 30,000 volumes.

"Good book dealers get involved with collecting mainly for their love of books and secondarily as a money-making enterprise," said Mrs. Sullivan.

Some of her prized purchases include the "Journal of the Expedition of Lewis and Clark" by Patrick Gass, published in 1808, the first printing of the first book by author and South Carolina poet laureate Archibald Rutledge, first edition Mark Twains and rare books on railroads and the Civil War.

"Dozens of times I spent a couple of hours looking through the books the Sullivans stored in their big Victorian home in Washington," said John Schulman, co-owner of Caliban Books in Oakland, an emporium of used and rare books. "Mrs. Sullivan had a great collection of Americana and sold her books at reasonable prices. Her husband was very gregarious and loved to tell jokes. They had a great relationship with other dealers and later made a successful transition to the Internet."

Three years ago, after Mr. Sullivan passed away, his widow moved from their Victorian home to a Washington townhouse. Although Mrs. Sullivan continues to buy and sell rare books, she recently decided to pare down her collection with the assistance of her daughter, Patricia Hollot of Peters.

"Some books I refuse to part with, partly because I might use them for research, partly because I enjoy them so much," she said. "I also have grandchildren I intend to pass them down to as well as family members, friends libraries and historical societies."

At the end of the catalogue segment of the auction, about 200 lot boxes of quality books will also be sold, grouped together by topics such as nature, the Civil War, Native Americans and Pennsylvania history. The auction, located at the corner of West Beau and Washington streets in Washington, is open to the public, which can come in at anytime during sale.

"It's always exciting for us to work directly with a collector because we can get a lot of insider information we might not get from someone representing an estate," said Tripp Kline, licensed auctioneer and owner of the Three Rivers Auction Co.

For Mrs. Sullivan, the book auction has a bittersweet component. "While it's a relief to sell off some of my books, it's also hard to see them go," she said.