Stick Fly, a new and robust play when Philadelphia-area audiences saw it four years ago at Princeton's McCarter Theatre, is now a new Broadway play, even stronger, smoother and more affecting.

The smart playwright Lydia R. Diamond has given Stick Fly added heft and juicer dialogue in several productions along the way, if I am accurately remembering the version four years ago, when McCarter Theatre was part of the play's development.

On Broadway, this look at an African American family with a big vacation home on Martha's Vineyard sounds very real, and has fascinating characters in a plot that keeps going strong through the last lines.

The current Stick Fly - whose title refers to a form of research among scientists who study bugs - is produced by singer-songwriter-actress Alicia Keys and directed with a snap-snap beat by Kenny Leon, who has another black-themed Broadway play running, The Mountaintop, a fantasy about the Rev. Martin Luther King Jr.

Since the 17th century, snug Martha's Vineyard, off mainland Massachusetts, has been home to an African American community as diverse as the rest of the island's residents - rich or famous, or merely fortunate or year-rounders. In Stick Fly, the summer of 2005 brings to the sprawling LeVay house (David Gallo's terrific mansion set) most of the family: the neurosurgeon father (Ruben Santiago-Hudson), his plastic-surgeon older son (Mekhi Phifer) with a new, white girlfriend (Rosie Benton), and his over-schooled younger son (Dulé Hill) who raises dad's hackles because he's chosen a fiction- writing career. That son brings his volatile fiancée (Tracie Thoms), whose late father is revered for his writings on racism.

Add to this a family friend (Condola Rashad) standing in for her mom, the maid, plus the family matriarch who throughout the play may or may not be arriving. In Stick Fly, after rapid character development that involve us with these people, Diamond weaves matters of race, mobility and family into a plot about folks with secrets large and small.

The superb cast gives impressive nuance to these characters, and the play is as funny as it is surprising - and, by the end, gripping, as refreshing as those waves that lap the Martha's Vineyard sands in August.

Contact staff writer Howard Shapiro at 215-854-5727, hshapiro@phillynews.com, or #philastage on Twitter. Read his recent work at http://go.philly.com/howardshapiro. Hear his reviews at the Classical Network, www.wwfm.org.

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Stick Fly: Playing at the Cort Theatre, 138 W. 48th St., New York.