In the Purcellville branch of the Loudoun County library system, there are books in nooks, books in crannies, books filling up the meeting room and books spilling across reading tables.

In fact, there are so many books--41,500, to be exact, or about 4 1/2 times what the building was designed to hold--that it's hard even to find a place to sit.

The chaos in the Purcellville branch, however, is symptomatic of the problems faced by the county system as a whole. For not only is Purcellville crowded but so is the tiny Thomas Balch library in Leesburg, which has more than five times as many books as it can hold. Even the Sterling branch, built in 1978, is already been filled past its designed capacity.

And, because there are no county funds budgeted for expansion, there is little hope for immediate relief.

"Our space problems are so acute, we're just struggling to keep up with the books," said Sally Hunt, Loudoun's library administrator. "There's little room for anything else."

Even though the county has increased the library budget dramatically since 1975--the year the current library system was created--many believe the county still does not spend enough.

Compared to other suburban counties in Northern Virginia, for instance, Loudoun lags far behind in its spending. While it boasts 120,000 books, Loudoun spends less than $13 per resident and has only 15,000 square feet of space. Arlington County, on the other hand, has 497,000 books, 110,000 square feet of library space and spends $22 per person annually, while Fairfax County has 1.4 million books, 223,201 square feet of space and spends $17 per person annually.

In an effort to come to grips with the system's shortcomings, the Loudoun Library Board of Trustees and the library staff recently convened a group of citizen advisers to help them formulate a list of priority improvement projects. But reaching a consensus on the kind of library system the county should have is proving difficult.

"It's hard for people to understand what a library could be without going through all the steps of planning it," Hunt said. "We are struggling with much of this, and it's hard to find a balance."

The library board already has requested $50,000 in the 1984 proposed budget to hire a consultant to develop a facilities plan. But the decisions about requesting capital investments from the county and where to make improvments may take months of work, Hunt said.

Differing opinions about the library system stem from Loudoun's diverse population and changing library needs. The population boom in eastern Loudoun, for instance, has resulted in an influx of well-educated families, many of them with children. That has created a demand for more sophisticated types of library services, such as videotapes and special reference materials.

But for north county residents near Lovettsville, any library at all would be appreciated. Many of them must drive for up to an hour to get to the Purcellville or Leesburg branches and are unhappy with the infrequent bookmobile visits, said Jeannine Reynolds, chairman of the library board. Citizens there have gone so far as to organize their own grass-roots library while they lobby for a county facility.

In a survey of people using the three Loudoun libraries early this year, residents said their top priority was improving the collection of books and films. But residents also said they wanted the libraries to provide more information and referral services, a need filled until recently by a federally-funded social service program.

Whether the libraries can be expected to fill gaps in community services, such as providing meeting space and educational programs, when the basic library system still falls far below the standards for libraries set by the Virginia Library Board is a question the citizens committee will have to consider.

Building a new library costs at least $30 a square foot and can go much higher, Hunt said. To build a facility the size of the library in Sterling would cost Loudoun at least $185,000. To build as much additional space as the Virginia Library Board says the county needs would cost at least $580,000.

But for a county facing heavy needs over the next decade for other capital improvments, such as schools and firehouses, any expense at all for the library system may be a difficult political battle to fight. That has led at least one member of the Board of Supervisors to suggest private groups be asked to fund any building plans the committee may recommend.

Hunt, however, said she thinks that is unlikely. "We need to depend on the county" for the basic space and staff requirements, she said. "Perhaps extras, like building an auditorium or special collections, could be provided through private funds."

If the citizens committee can reach agreement on recommendations, their suggestions will be forwarded to the library board later this year in time for the board to request capital improvement funds as part of the 1985 county budget.