More accustomed to the leisurely expanse of a novel, writer Nick Hornby delivers an economical screenplay for An Education — a film as acutely intelligent about the wiles of young love as his novel High Fidelity was about old love.

Adapted from Lynn Barber’s memoir about 1961 England, An Education depicts how ideas steeped in popular culture and pie-in-the-sky predictions for our futures can sock even the most sensible among us. It also represents the major arrival of Carey Mulligan, a young actress with enough poise, professionalism and presence to immediately place her among the very best of her peers.

Mulligan is Jenny, an intelligent teenage girl primed for the primrose path of prestigious collegiate education. She’s an accomplished cellist and straight-A student — a “joiner-inner” as her parents Jack (Alfred Molina) and Marjorie (Cara Seymour) would say.

An essay on Jane Eyre earns Jenny an A+, fitting given that she’ll have to work out her own moral fiber through a test of how far her independent streak will go. Rather than the men in her life trying to subjugate her, they’re just unable to come clean about what they want.

Jenny’s obsession with French-chic culture portends dissatisfaction with proper expectations. And it’s precisely why Jenny is drawn to David (Peter Sarsgaard) when he pulls up alongside her and offers her cello — and then her — a respite from the rain.

Hornby and director Lone Scherfig (Italian for Beginners) turn this meet-cute on its ear with the mere circumstance of David’s age. He’s clearly in his 30s, which is slightly creepy but not entirely off-putting.

Right away, David is the trickiest character Sarsgaard has ever played — someone by whom we’re charmed but also a little repulsed. There are plenty of crumbs to suggest David is a wolf at the door, but we’re swept up by his sweet seduction right along with Jenny.

He is all that the awkward boys Jenny’s own age cannot be, lavishing poetic praise on her intelligence with ineffable charm and delivering seemingly genuine insinuations and intimations about their future. In David, Jenny sees access and elevation out of what she perceives to be a future filled with dreary academia.

With David, Jenny’s schoolgirl sensibility bumps up against her sexual awakening, and Mulligan provides unwavering structure to the decade’s most realistic depiction of a smart, budding teen girl coming of age. She’s got Katie Holmes’ scrunchy cheekbones with the lithe stride of a long-lost Gyllenhaal — in other words, classically beautiful.

Scherfig capitalizes on Mulligan’s features for how she frames Jenny’s graceful glides through David’s seemingly bourgeoisie lifestyle of weekend getaways and all-night outings with friends Danny (Dominic Cooper) and Helen (Rosamund Pike).

Eager to please and fit in, Jenny subsides in the spaces between them — in their orbit, but at its very perimeter. And there’s detached artifice among the whole group — Jenny and Helen’s hair respectively swept up like Audrey Hepburn and Catherine Deneuve (in a nice cinephile touch).

It’s indicative of how David and Jenny’s courtship is fraught with tension — not so much because of any tawdry predatory nature, but from the opportunity costs of what a life with him would mean for her. Weighing what must be traded off to achieve a popular perception of prosperity makes An Education an arthouse cousin to Whip It.

Soon enough — and to Jenny’s surprise — Jack and Marjorie are goading her into the good life with a man they find worldly, tolerant and, most of all, financially self-assured.

Jenny believes her love for David is a foregone conclusion as lasting forever. But, in a way, David is a better alternative for Jenny’s parents than he is for her — a booby hatch out of perhaps-insurmountable financial debt from school. The question is how emotionally corrosive Jenny’s, Jack’s and Marjorie’s decisions, and discoveries, about David will become.

Of course, this is after David is revealed to be a particular brand of louse. (After all, there would no education of which to speak without that.) However, Hornby’s screenplay never vilifies him. It’s strangely empathetic about at what point pursuing youthfulness should end for a man insisting he can have endless first times. His seems a charmed life but it’s anything but, and he’s seeking escapism as well.

More dangerous than fancying herself the expert before learning the lesson is whether Jenny will choose the perilous, deadened path of shielding herself from the hardest knocks. Jenny’s success will depend on whether she — and her parents — can seize upon their strengths rather than slacken for stability or a safe bet.

Molina’s showcase scene — which should alone earn him an Oscar nomination — comes with a quietly devastating, tough and poignant bedroom-hallway confession to, and consolation of, Jenny. In that moment of one of 2009’s best films, you see a family collectively come to appreciate the strength of a heart scarred over and the true blossoming of a woman.