Celia Keenan-Bolger, Colin Donnell, and Lin-Manuel Miranda Photo by Joan Marcus.

This will be, for those at various stages of involvement, the culmination of many dreams. This is, among other things, the first Encores! production slated to run two weeks, through February 19, an admission that there's interest (or perhaps a plan) for this show that transcends the typical. Then there's that this one is, quite unusually, being performed essentially whole, with director James Lapine (also providing the "concert adaptation") not hacking and slashing the book in favor of a heightened focus on the songs. And, oh yes, this is also one of the most lavish mountings of the series to date, with set (John Lee Beatty), costume (Ann Hould-Ward), lighting (Ken Billington), and projection (Wendall K. Harrington) plots so elaborate, that they all look like part of a brightly wrapped, ready-to-transfer package.

Beneath all that surface slickness, however, is a pervasive lifelessness that keeps the combustible elements from fully igniting. You first sense it in the overture, which despite Jonathan Tunick's high-octane orchestrations sounds, under the ministrations of music director Rob Berman and the Encores! orchestra, more like a wall of horn-heavy blare than a searing evocation of the story's conflict of Broadway art colliding with Hollywood commerce. Then, when we lope into the prologue, it's a sedate, crisply informational affair in which the crooning chorus members appear more interested in staying out of the way of the lickety-split-changing LED backdrop as it displays its era-defining headlines and myriad Photoshopped snapshots than they do musing on the fluid and flummoxing nature of time. Already, something's wrong.

The unease continues as the action transitions into a reception celebrating the first major studio release from an up-and-coming producer named Franklin Shepard (Colin Donnell), a gifted composer gone movie-mainstream. He's rich and happy or, you might say, rich and "happy," with a glittery wife named Gussie (Elizabeth Stanley) he can't stand, a mistress he's content to ignore, and a best friend named Mary (Celia Keenan-Bolger) whose idea of a party is getting smashed and insulting her host. Here, too, the chemistry is off, with the exchanges steaming rather than crackling, the staging indifferent, and Keenan-Bolger utterly unable to convince as, and even seeming to psychologically rebel against, the middle-age malcontent who's got a Dorothy Parker–style retort for every Southern California bromide she encounters.

Moments like these, dotted with rocky pacing and unsteady delivery, are plentiful as we travel ever further back to meet Frank's estranged songwriting partner, Charley (Lin-Manuel Miranda), ex-wife Beth (Betsy Wolfe), and producer-discoverer Joe Josephson (Adam Grupper), who have all played key roles in making Frank the artist, and then the shell, he became. Lapine and his cast have consistent difficulty connecting with scenes and Furth's sometimes too-arch dialogue, often polishing up their smoothly moving exteriors but seldom peeking underneath. This problem is only amplified by the inclusion of so much dialogue you can't see this evening as the kind of music-oriented event most Encores! shows satisfy themselves with being; it plays as if it wants to be the Real Deal, and at that it's too empty to succeed.

There are pleasures to be found, of course. Dan Knechtges's dances are refreshingly subtle, for one thing, and as mentioned the show looks terrific. Then there's Sondheim's score, one of unusual verve and bounce as it charts young adulthood's maturation into midlife . It captures the excitement of friendship ("Old Friends"), unplanned independence ("Now You Know"), and burgeoning adulthood (the intricate musical scene, "Opening Doors"), all blended against expectation and heartache rendered both organically ("Not a Day Goes By") and theatrically ("Good Thing Going"). With chunks of music and lyric that constantly reassemble themselves like components in a factory, the songs have no trouble demonstrating the surprising ways the past can inform the future.

But for Merrily We Roll Along to work, all the other pieces must be on the same page. Lapine and his cast haven't found sufficient reasons for us to like, or at least sympathize with, the self-involved and self-implosive characters we see, which subverts a story that already trends too much toward a cautionary tale of "selling out."

In showing how Frank slowly develops his inner grease, Donnell does more than anyone, and is the only performer whose characterization fully seems to grow in reverse. Coming close are Stanley, sturdy and smoky as other woman–diva Gussie; Wolfe, who projects the proper enterprisingly flighty niceness as Beth; and Grupper as a brusque and effective Joe. But Keenan-Bolger's Mary is rollickingly unfunny, landing none of her booze-drenched-yet-parchment-dry quips (and sounding underequipped for her rangy songs); and Miranda, best known for writing and starring in In the Heights, is not a natural nebbish, with his attempts at forcing the issue (particularly in Charley's televised breakdown, "Franklin Shepard, Inc.") and borderline-untrained singing voice making the character look unhinged rather than unappreciated.

Things click only really during the final scene. Set on the rooftop of a Manhattan apartment building on the night of the 1957 Sputnik launch, it unites Frank, Charley, and Mary for the first time to gaze at the sky and question what the world—and they—will become in the years they'll witness. Their commemorative song for the event, "Our Time," bursts with near-childlike anticipation, one of the few feelings that Donnell, Keenan-Bolger, and Miranda are all able to project equally well. The scene is not as haunting as it should be, given the ghosts you've seen that they haven't, but it's as fresh and sparkling as the trio's hopes, and after the flat-Champagne feel of the rest of the preceding two and a half hours, that's not nothing.

It's enough, in fact, to make you believe, in case you've forgotten as you've grown older and more cynical yourself, that wonderful things are not necessarily an impossibility after all. It's a fine message, worth remembering, and one that this Merrily We Roll Along communicates exceedingly well. But it might mean a bit more if the rest of the production didn't have so much trouble saying anything at all.

Encores!: Merrily We Roll Along
Through February 19
New York City Center, West 55th Street between 6th and 7th Avenues
Tickets online and current Performance Schedule: www.nycitycenter.org