The District's chief librarian, Ginnie Cooper, says there was no concerted effort to make the four libraries built in the past two years all look the same. No effort to produce a modern version of the old Carnegie-style libraries, which brought classical dignity and patriarchal solidity to the idea of "library" all across America around the turn of the last century. No effort to "brand" them like a chain of restaurants or coffee shops, the all-too-fashionable trend in contemporary architectural thinking.

But with Monday's unveiling of the new Tenley-Friendship Library on Wisconsin Avenue, it's clear that a coherent style has emerged, if not intentionally, then organically, in the four stand-alone, built-from-the-ground-up buildings that have replaced some of the most obsolete and ugly of the District's 24 neighborhood facilities.

The new branches on Benning Road in Northeast Washington and on Good Hope Road in Anacostia (both finished in April), the Watha T. Daniel Library in Shaw (opened in August) and the Tenley-Friendship branch express similar ideas about form and materials. They are clean, sleek, contemporary buildings, with appealing geometry, and are clad with materials that suggest a mix of industrial chic and environmental sensitivity. For different reasons, they stand out in their neighborhoods, so much so that it is as easy today to look at them and instantly think "library" as it was when Andrew Carnegie was building his compact palaces of knowledge in dusty cow towns and aspiring megalopoli alike.

That contrast - the powerful sense that something new has arrived - is one of the best things to happen to the District, architecturally, in decades.

The Tenley-Friendship Library is the most expensive of the new branches, although the renovations of the burned-out Georgetown branch were even costlier. It cost $18 million to design, build and furnish, which is about $3 million more than the average for the newly built branches. It dominates its oddly shaped polygonal patch of land at Wisconsin and Albemarle Street NW, a large, rust-colored form with an appealing and repetitive screen of vertical sunshades along its south and east faces. A small plaza with benches and concrete planters meets the street, offers handicap access and helps integrate the building into the slope of Wisconsin (the highest ground in the District, a whopping 409 feet above sea level, is only a few blocks away).

The library is divided into "front" and "back" of house spaces, with the stacks and most public areas contained in two large, well-lit front rooms clad in glass. A green roof, not accessible to the public but a boon nonetheless, covers the stacks and a central, glass-covered spine connects the front of the library to the rear volume, which holds meeting rooms, offices and a children's story room.

Long-standing efforts to develop the site as a mixed-used facility with commercial space never materialized and delayed design and construction. But the new building has been engineered to accommodate a large new neighbor above it. Giant square columns have been relatively well-concealed in the back of the library and could support several floors of new space if the city continues to go forward with intelligent plans to densify the real estate near its Metro stations. There have been complaints in the neighborhood about these smart-growth plans, but those complaints are the worst sort of NIMBYism. Where else should the District grow if not along its historic commercial corridors and near its vital public transit nodes?

The building was designed by the Durham, N.C.-based Freelon Group, one of the architectural firms that is partnering with David Adjaye to design the Smithsonian's National Museum of African American History and Culture. Freelon also designed the Anacostia branch, and based on these two buildings, it's clear they have some work to do when it comes to finishing the details of a building. The outsides are handsome. Inside, there are awkward moments.

In the Anacostia branch, a staircase connecting the lower, parking level with the upper, main floor of the library creates a large amount of wasted space underneath, enough to have added several private reading carrels. In the Tenley-Friendship facility, sliding glass partition walls haven't been thought through carefully enough. On the ground floor, when opened, the retracted glass panels block a door (which is used only when they're closed, but still, it looks stupid). On the second floor, when closed, they form a gap between the exterior wall of the library, large enough for a child to slip into. That problem will be fixed, but it suggests that some design elements are more improvised than strategized.

The children's reading space at Tenley is also one of the least appealing among the newly built libraries, a windowless room distinguished only by some jazzy, semi-spherical lighted ceiling coffers. Children at Benning, for instance, can snuggle into their own semi-circular, naturally lit fantasy space; at Tenley-Friendship, they just get a box.

If the designs from the Freelon Group aren't as polished as the libraries designed by Davis Brody Bond Aedas (its two-floor, glass wedge in Shaw is the standout of all the new libraries), they are much better than the buildings they replaced. And they are distinctly more interesting than most of the architecture nearby.

All of the new buildings, each in its own way, rise above their context. Anacostia is a trim box of glass with a green cap and luminous light tower, in a landscape of forbidding and dilapidated structures. Benning exudes a sense of urbane seriousness in a suburban-style commercial landscape. Shaw commands its triangular lot with confidence and airy openness and offers a particularly good view of the city on three sides. And Tenley-Friendship is a rare, civic structure, built with a freedom of form that distinguishes it from a long strip of functional shops, supermarkets and cafes.

There are two more stand-alone new libraries to open, the Francis Gregory branch in Southeast and the Washington Highlands branch in Southwest, both under construction, both designed by Adjaye. And there are two major renovation projects, in Mount Pleasant and Petworth, scheduled for completion this year. But with Tenley, and with a new mayor and sobering new financial realities, there is a sense that an exciting chapter of civic regeneration may be coming to an end. Cooper would like to do more.

"I'm very concerned about a capital maintenance budget," she says. And she has a wish list for improvements, with Woodridge in Ward 5 and the Northeast branch on Seventh Street at the top. But it's all up in the air.

But, a few details aside, it has been a remarkably successful campaign. Libraries are rare common ground on the fractious map of democracy, a place where traditional ideas of bootstrap self-improvement meet liberal ideas of open access and equal opportunity. Few encounters with local government - a labyrinth of red tape, taxes, frustration and long lines under fluorescent lights - feel so good as an afternoon in a well-run library. Without lecturing or hectoring or cheap rhetoric, they build consensus and commitment to self-governance.

There is an enormous capital investment in the District's library system. The overall improvement campaign, which includes smaller renovations across the city and has cost $120.5 million since 2004, is only part of that investment. There is also a stored human and cultural capital in its books and other materials, and in the rare sense of goodwill built over decades in the community.

These buildings might have looked a lot more like Starbucks or Whole Foods, more slick debit-card modernism making life blandly comfortable. They might have suggested an old-fashioned pomposity and grandeur. They might simply have been dull and meaningless. But by design, or accident, or some mix of both, the architects who have contributed to this project have managed to make libraries that are in their own way every bit as inviting, serious and inspiring as the libraries of yore that helped forge a new middle class out of a Babel of huddled masses more than a century ago.