Gunn, whose credits also include HBO's "Deadwood" and "The Practice," plays Oliva opposite Magnussen (The Ritz, "Into the Woods") as Ethan in the drama, which runs through Aug. 24 at Second Stage's Tony Kiser Theatre.
Opening night is set for July 30 as part of Second Stage Theatre's 35th anniversary season.
Here's how the drama is billed: "How far will you go to get what you want? Will you be the same person if you finally do? When star sex blogger and memoirist Ethan tracks down his idol, the gifted but obscure novelist Olivia, he finds they both crave what the other possesses. As attraction turns to sex, and they inch closer to getting what they want, both must confront the dark side of ambition and the near impossibility of reinventing oneself when the past is only a click away."
Playwright Eason's other works include The Adventures of Tom Sawyer, Around the World in 80 Days, Rewind, The Vast In-Between, Remarkable Invisible, Every Reason To Hope and Believe and The Undeniable Sound of Right Now, among others.
Other members of the creative team include set designer Andromache Chalfant, costume designer ESOSA, lighting designer Japhy Weideman, sound designer Fitz Patton and production stage manager Scott Taylor Rollison.
Second Stage's Tony Kiser Theatre is located at 305 West 43rd Street. For more information and tickets, call (212) 246-4422 or visit 2ST.com.