Composer-lyricist Adam Guettel was viewed as a Broadway wunderkind when his musical The Light in the Piazza debuted in 2005 — so long ago that Encores! is mounting a revival later this month. But after several projects foundered, Guettel returns this month with his first full musical in nearly two decades: an operatic adaptation of the 1962 Jack Lemmon-Lee Remick movie Days of Wine and Roses.

The Oscar-winning theme tune, a Henry Mancini-Johnny Mercer standard, is completely absent from this two-hour, intermissionless show, which opened Monday at Off Broadway’s Atlantic Theatre Company. Instead, Guettel delivers a score that makes up in tricky chromatic phrasing and time signatures what it lacks in harmonic earworms. The approach may be deliberate since the subject is a love triangle involving a glad-handing PR executive (Brian D’Arcy James), a secretary turned stay-at-home mom (Kelli O’Hara) and the paramour who threatens to undo both of their lives: alcohol.

Guettel reteams with Piazza book writer Craig Lucas, who follows the major downbeats of the movie with almost slavish devotion, and Kelli O’Hara, here taking on the Remick role as the chocolate-loving teetotaler whose introduction to the Brandy Alexander by D’Arcy James’s Joe leads her on a downward spiral from which she is unable to recover despite the efforts of Joe, her stalwart father (Byron Jennings, oddly deprived of his own song) and their young daughter (Ella Dane Morgan, who delivers an impressive vocal performance).

The fortysomething O’Hara may seem slightly too old to play the innocent ingenue in the rushed early scenes, which Lucas and Guettel speed up to get to the dissolution that forms the core of the plot. But the hurried opening minutes also make it hard to see what drew these two addictive souls to each other aside from the appeal of their third wheel, a love affair that gets a jazzy minor-key treatment in the duet “Evanescence.” Later, D’Arcy James and O’Hara are in magnificent voice for their dueling solos “Forgiveness,” where the quest for AA-approved serenity proves dauntingly elusive compared to the object of other aspirational anthems in the musical theater canon.

Director Michael Greif’s production is a stylish and efficient one, thanks to Lizzie Clachan’s urbane sets, Dede Ayite’s Mad Men-era costumes and Ben Stanton’s effective lighting. D’Arcy James and especially the luscious-voiced O’Hara sound fantastic performing Guettel’s dauntingly complex score. But this is an off-putting exercise on both a narrative and a musical level — one that may leaving you pining for less wine and many more roses.