This new musical, now in previews at Playwrights Horizons, tries so hard to be likable that I am feeling guilty that I am unable to surrender uncritically to its charms. Three graduate drama students at Yale (Will Connolly, Michael Mitnick and Kim Rosenstock) wrote it for a student production five years ago. It has since been produced in Palo Alto and Dallas, where it received enthusiastic reviews. Its plot concerns Harold (Adam Chanler-Berat), a nerdy young sandwich maker in New York who falls for two sisters from South Dakota — Daphne (Patti Murin), a bubbly extrovert who wants to make it as an actress in New York, and Miriam (Allison Case), the introverted older sister Daphne has dragged with her to New York, who enjoys being a waitress and would rather be back home looking at the stars. That’s my first problem: the two sisters are such complete opposites that I found it hard to believe that anyone could fall for both of them. In addition to the central triangle, we meet Harold’s recently widowed father (the always excellent Peter Friedman), his cranky boss Crabble (the fine Michael McCormick); Joey Storms (Bryce Reness), a wealthy playwright/producer/director who takes Daphne as his muse, and, finally, the narrator (the admirable Henry Stram), whose various roles include the sisters’ mother and a gypsy fortune teller, and who keeps the audience apprised of the play’s many time shifts back and forth during the year leading up to the great Northeast blackout of 1965. My second problem with the show was that I didn’t find the central characters nearly as interesting as the people who surround them. Harold’s father and his boss are considerably more vivid than Harold. Why Harold behaves so thoughtlessly to his father was not clear. The sisters seemed more like bundles of characteristics than characters. The music, played by an onstage band of four, is serviceable and perhaps more than that for those who like rock. There is one ditty that you will have trouble getting out of your head. The authors are skillful at knitting their material together: a song heard early on develops entirely new meaning by the time it returns. The climactic blackout is a well-played narrative device to knit many strands together. I give the authors credit for not flinching at presenting moments of sadness. The second act, after a promising start, began to drag. I think the play would gain from a substantial trim that would allow it to be performed without an intermission breaking the flow. The uncluttered unit set by David Korins is quite attractive. Jeff Croiter’s lighting design adds much to the play. Paloma Young’s costumes are appropriate. Carolyn Cantor’s direction is fluid. It’s hard to imagine a better production. Whether the slightness of the material can support this deluxe treatment is another matter. Running time: 2 hours 30 minutes including intermission.