In the current popular culture, female friendships—at any age—are generally considered secondary to life's "important" relationships, the romantic bonds between men and women.

Nowhere is this depressing trend more evident than in Hollywood, where story lines putatively about women's friendships tend toward the saccharine ("Mona Lisa Smile"), the malicious ("Mean Girls") or the boy-crazy (take your pick).

Which is why it's such a pleasure (and a relief) to encounter movies such as "The Sisterhood of the Traveling Pants 2." Like the first "Pants" movie, it presents its heroines' relationships as complicated, challenging and particularly rewarding, and not simply as a vehicle for finding the perfect boyfriend.

The four stars of "Sisterhood" are back for this smart, confident second act, based on novels by Anne Brashares. They're reprising their roles as best friends who share a remarkable pair of blue jeans—which, you'll remember, mysteriously transforms to fit each of them whenever she needs its powers most.

Whether the jeans actually perform miracles or simply boost the wearer's self-confidence is a moot point; for teenage girls, the latter is akin to the former.

As the movie opens, we find the friends (Carmen, Bridget, Tibby and Lena) at the end of their first year in college; Carmen (America Ferrera, appealing as always), still the group's emotional center, is looking forward to a summer at home surrounded by her best friends, but the others have different plans. Tibby (the enormously talented Amber Tamblyn) is staying in New York to work on her screenplay, and Lena (Alexis Bledel, formerly of "Gilmore Girls") has signed up for summer classes at the Rhode Island School of Design. Meanwhile, Bridget ("Gossip Girl" Blake Lively) is off to Turkey on an archaeological dig. Stung by the abandonment, Carmen joins a high-profile summer stock theater program in Vermont, where she is quickly recruited from behind the scenes into the spotlight.

Screenwriter Elizabeth Chandler, who also penned the first "Sisterhood" installment, wisely hews close to the formula that made the previous movie a success, and director Sanaa Hamri ("Something New") keeps things moving at a good clip.

This is an ensemble piece, but the young stars are each entrusted with a complete, largely individual story arc, a challenge they handle with various degrees of success: Tamblyn, whose Tibby is sarcastic and very funny, is the clear standout, imbuing her most brittle exchanges with humor and a tentative warmth. Ferrera, taking a break from the relentless cheeriness of "Ugly Betty," has become a mature, highly nuanced performer. Meanwhile, Lively's Bridget is like a sunny day threatened by storm clouds; her slightly manic high spirits feel a bit dangerous. Hers is by far the most dramatic story line, and Lively seems a bit overwhelmed at times, but she turns in several very nice scenes with Blythe Danner, who plays her estranged grandmother. As for Bledel, I can't decide if she's an incredibly subtle actor, or if she's only capable of two facial expressions (vague confusion and vague happiness).

Watching the adventures unfold, I was reminded of the "Sex and the City" movie—not only because "Sisterhood' also features four independent, pointedly distinct characters who aren't perfect, as friends or as people, but who make brave attempts at being the best possible versions of both—but because both films belong to that rare breed: movies whose sole focus is a largely realistic iteration of evolving, empowering female friendships.

That's not to say there aren't boys on the scene; in fact, there are plenty of exceptionally cute, smart, kind guys to be had—in the life drawing class, onstage in Vermont and even in Manhattan's West Village. But while the romances are great fun to watch, they never take over the movie, even in their most dramatic, angst-ridden moments.

And while there's an element of fantasy to much of the movie, serious issues, including teen pregnancy and mental illness, lurk beneath the cinematic sheen.

Nothing about this movie feels revolutionary, but don't let its easy charm fool you. Like its predecessor, "Sisterhood 2" is based on two radical ideas: namely, that young women's stories are about more than the pursuit of men, and that happiness isn't something someone else gives you—it's something you have to find for yourself.

See the trailer and find local showtimes for "The Sisterhood of the Traveling Pants 2."