It was a balmy springlike evening last night as my friend Amanda and I stood outside the Booth Theater on West 45th Street. We were having a quick chat before going inside to see Vanessa Redgrave perform in The Year of Magical Thinking, Joan Didion’s new play adapated from her best-selling memoir.

Who should we spot standing next to the theater’s entrance but author Philip Roth in a black suit and a lot taller than I had imagined him to be. And then here came British playwright David Hare (Plenty, Via Dolorosa). He was carrying two notebooks and quickly entered through the stage door. He was the show’s director and, since the show had just started its previews, was obviously going to give Vanessa her notes after the performance.

The play doesn’t open until March 29 but here’s my early preview for those unlucky enough not to have bought tickets to what may be a sold-out limited run. The tall and imposing Ms. Redgrave does not physically resemble the tiny and frail-appearing Ms. Didion, but for almost two hours (without an intermission), the audience sat enraptured and moved as the splendid Redgrave captured Didion’s shock, grief , and denial (”magical thinking”) in the wake of her husband’s sudden death and her only child’s devastating illness.

The play is not an exact transcription of the book as it covers events that occurred after the memoir was published, notably daughter Quintana’s death in August 2005. In a Playbill interview, Didion said she approached the play not as a simple adaptation but as a fresh work, noting that the character Redgrave plays “is speaking from a year and half or two years later. It’s a different perspective.”