The Pohick Regional Library rises like a bright, curious civic surprise from a hollow near Old Keene Mill Road -- pretty much what the Fairfax County government wanted in fast-growing Springfield. It's a flawed building but appealing, ingenious -- a piece of '50s functionalism dressed up with color, decoration and a bit of romance in the form of yellow-topped, hexagonal brick towers.

"There's a feeling out here that the county government is far away," says Eason Cross Jr., its architect, "so the main goal was to establish a visible symbol."

This was easier said than done, because other requirements -- for books, stacks, meeting rooms, offices, study areas, electronic equipment and the like -- dictated a no-nonsense single-story box unfortunately situated on a low, four-acre site that angles onto a winding, four-lane rush-hour road.

Two additional requirements -- for solar energy and a high-ceilinged interior space -- provided the architect with critical clues to solve this seemingly contradictory puzzle. Because of parking, drainage and other needs, the position of the basic box was a given: It aligned itself on a diagonal with the beckoning southern sun. Cross simply (and smartly) bisected the box on this line and pushed up his solar wall there.

The wall, then, does double duty. Glazed on the south to receive the sun's heat, it also provides a structural anchor for the giant steel beams supporting the stepped, ribbon-window skylight system facing the building's entrance on the north. These beams, sheathed in painted gypsum board and arranged in a dramatic fan pattern, are the distinguishing feature of the attractive (though slightly disorienting) "general space" indoors.

Had Cross stopped here, though, the result would have been a fairly conventional, structurally expressive modern building of a kind he was schooled to do under Walter Gropius at the Harvard Graduate School of Design in the early 1950s. Instead, he made three additional moves that enable his building to contribute to present-day architectural discourse.

First, because a rectangle bisected on the diagonal forms two triangles, he made the triangle the basis not only of the floor plan but also of an inventive ornamental scheme. There are triangles everywhere one looks here -- reading areas amid the stacks in the low-ceilinged portion of the building are open to triangular skylights; bay windows are triangular in plan; porcelain enamel fasciae are triangulated; even the carpets have tiny three-sided flecks.

Second, to symbolize the solar element that played such a major role in the design, he chose yellow as the basic decorative color. It, too, is omnipresent, though occasionally so putty-dull that its symbolic significance is weakened, if not altogether lost.

Finally, and less predictably, he conceived the hexagonal towers. Located at two corners of the building and at either end of the solar wall, these have a certain functional-esthetic justification -- they contain heating, cooling, electrical and other kinds of equipment that otherwise would have despoiled the low roof.

But they also symbolize the civic purpose and give the building visibility. The most important of the four because it's next to the principal entrance, the northern clock tower is appropriately the most expressive -- even with its bright yellow, triangulated crown it's a brooding, somewhat medieval piece.

Unfortunately, the various parts of his Pohick Library do not quite add up to a cohesive whole. The site isn't a great help -- it's so low that the public building is overshadowed by a complex of nondescript commercial structures recently erected nearby, on higher ground. The proportions of crown to tower are off -- the clock tower, especially, seems unhappily truncated. There are bits and pieces -- the enamel frieze, for instance -- that seem tacked on. The relationship of stuccoed to brick wall surfaces is uneasy at best. And opportunities for public art -- figurative, abstract, site-specific ... anything -- were somehow passed over.

It is interesting to compare this late-'80s library with the Watha T. Daniel branch library that the same firm, Cross and Adreon, designed in the mid-'70s at Eighth Street and Rhode Island Avenue NW in the District. Though it, too, is an intelligently planned and workable library, it's definitively of another architectural age. I've always found its symbolism appalling -- it's a bunker, a concrete fortress, a` la late-period Corbusier, in the middle of the city.

The distance Cross has come between then and now is suggested in his observation, vis-a`-vis the Pohick Library, that "contemporary architects for the most part still hold to the dictum that form ought to follow function, within contextual limits, and with no obeisance to any stylistic straitjackets." But, he continues, "we are also regaining the use of that formerly paralyzed arm, ornament and decoration, used with restraint and on purpose."

In other words, Cross maintains allegiance to his modernist roots but he's seeking ways to enrich the vocabulary without employing historical styles, except in the most general way. This is a defensible, even an honorable, position, but it needs to be pushed further than he was able to go with the Pohick Library, a building that suggests more than it actually delivers.