"Each of us who loves the theater,” writes John Lithgow, “has a secret list of the great shows we never got to ­see.”

His may be. Mine’s not. I would love to have seen the original Long Day’s Journey Into Night or Agnes DeMille’s choreography busting out all over the premiere of Oklahoma! or Alla Nazimova, said to be the greatest actor of the 20th Century, perform live, regardless of the vehicle. Throw in Shakespeare’s Hamlet, of course, and Sophocles’s Oedipus the King, not just for my Greatest Hits collection, but to stand elbow-to-elbow with the groundlings, or sit on hard marble with 4000 Athenians, and live the live ­event.

The sad fact of theater: when a show closes, it’s gone. Even videos can’t bring back the palpable rapport between actors and audiences or the “theatrical magic” that all but elevates the house. Filmed productions are like postcards of the Grand Canyon. The great ones only exist after the fact in writing and ­recollections.

Laurence Senelick edited a compendium, The American Stage, in which 78 authors, from Washington Irving to Tony Kushner, talk about the theater of their time. The text includes obvious choices — Stark Young, Dorothy Parker, Brooks Atkinson — but also names not associated with the stage — Walt Whitman, Willa Cather, Thomas Wolfe. These outside-the-box voices write with other than a mainstream approach or ­vocabulary.

Whitman — who knew? — was a theater junkie. He absorbed it “with every pore.” In three short articles, he rants about the vulgarity of the New York stage and its critics (“slaves of the paid puff system”). Usually when critics write about the audience, it’s an evasion: they haven’t a clue about the play. When he recalls the Old Bowery Theatre of the 1830s, Whitman seats you in the rowdy, smoke-thick auditorium, next to James Fenimore Cooper, flush-faced mechanics, and “types that never found their Dickens or Hogarth or Balzac, and have pass’d away unportraitured.” Their applause is an “inimitable and chromatic ­tempest.”

Written in 1885, the essay also reveals its author’s tastes. He first saw his favorite actor, the allegedly insane Junius Brutus Booth, in 1835, giving bullish declamations. But for the young Whitman, Booth taught a master class in artistic expression: “the words fire, energy, abandon, found in him unprecedented meanings.” Twenty years later, Whitman published Leaves of Grass, to which the words apply with equal ­fervor.

American Stage has received mixed reviews: it isn’t scholarly enough (or too scholarly and only for academics); it favors eras other than our own. All true, if Senelick meant to compile yet another high-toned salmagundi of the ­thea-tah.

But the book’s doing something different. Drawing from reviews, diaries, essays, and letters, it gives readers the spirit of the times, the writers’ urgency, and often the feel of the room during a ­performance.

Among these is playwright Morton Eustis’s classic about George S. Kaufman directing The Man Who Came to Dinner — still required reading for anyone interested in theatrical ­craft.

Kaufman rehearsed plays backwards, from the last act to the first. He did it, he says, to make sure each can stand on its own and to catch “dead” spots. “You think you have a script as tight as possible.” Then in rehearsal “dead chunks appear all through it.” In front of an audience “a whole new set of dead spots turn up. And three weeks after the New York opening you still find places you can ­cut.”

Kaufman utters insights throughout. They sound familiar: as when he tells an actor, “The moment you smile, the moment you think you’re funny, it’s gone!” But many originated with Kaufman. People have repeated them ever ­since.

Senelick resurrects writing that might otherwise be lost. Even though Brooks Atkinson called him “the best critic Broadway ever had,” few today have heard of James G. Huneker (1857–1921), who said he didn’t “take criticism as seriously as I do manslaughter or prohibition.” American Stage includes his perceptive piece about Frank Wedekind, which praises and cavils (“the dramatist in him is hampered by the theorist who would ‘reform’ all life”) and brims with Huneker’s acerbic voice: “If a critic can’t become famous because of his wisdom, he may nevertheless attain a sort of immortality…by writing himself down as an ­ass.”

For contrast, the anthology also offers atrocious critical writing. “There is a curious elation in his work which its subject matter could not engender. Whatever happens to the characters [the author] will come out rich and famous, and the play merely an episode in [his] career.” Thus spake Mary McCarthy on Tennessee Williams’s Streetcar Named ­Desire.

Another surprise: among essays about musicals and high drama, the eclectic anthology offers portraits of street theater, vaudeville, minstrel shows, and a charming piece by Walter Kerr on summer stock called “Barns”: “Even if the show isn’t very good…you don’t come out feeling ­cheated.”

Most prose about Alla Nazimova reads as if written across the street from the theater — or, more likely, on a hair-pulling deadline — and fails to elucidate her gifts. Djuna Barnes’s five pages on Nazimova are among the most remarkable in American Stage. Three quick tastes: “She wore a good ten yards of that slinky material which, when molded about the hips, spells a woman bent on the destruction of the ­soul.”

“One can see her longing in her every fiber to play parts that called for overtones and ­underacting.”

“She has the intelligence to know that quietly the world was made, and quietly it turns its sterner ­cheek.”

The book may not be for academics but, at almost three inches thick, it provides a thorough course on American theater. Many selections exude the passion of love letters, be it ardor or cosmic betrayal. If you lie awake nights worrying about the future of live theater, American Stage makes a fitting bedside companion. You’ll find yourself among ­friends. ■