“Natasha, Pierre & The Great Comet of 1812,” Dave Malloy’s immersive, festive and introspective electro-pop opera dramatizing a small portion of Tolstoy’s “War and Peace,” has undergone a most unusual journey over the past four years, moving from a small off-Broadway venue to a large tent to, finally, Broadway.

Along the way, it has grown considerably in size (adding more choreography and an ensemble) and gained two new leads: Denée Benton (who replaces Phillipa Soo of “Hamilton”) and singer Josh Groban (who replaces Malloy).

The show begins with a jamboree-like opening number where the young, spirited cast welcomes the audience, warns that the show is based on “a complicated Russian novel” and introduces each character.

In brief, the innocent, spoiled Natasha (Benton) and hunky, careless Anatole (Lucas Steele) engage in an affair (even though she is engaged and he is married) that ends badly. All the while, the rich but socially awkward Pierre (Groban) searches for meaning in life.

It truly is an opera (with sung-through scenes and arias instead of traditional songs) version of a novel (with plenty of exposition, long conversation and quiet meditation). Since it premiered, I have always found the show to be extremely uneven, with a stop-and-start momentum that alternates between all-out liveliness and long episodes of slow tedium.

That being said, Rachel Chavkin’s stunning production is an intoxicating whirlwind of wild activity. The Imperial Theatre has been dramatically reconfigured into a multilevel wonderland that evokes a war zone, upper-crust society and a trendy nightclub.

Many audience members sit onstage and performers use interior staircases and pathways to roam the orchestra and mezzanine levels.

Benton, a little-known actress, is wonderful as the doe-eyed Natasha, and Groban, with his rich voice in tow, gives a sensitive performance that fully captures Pierre’s angst-filled personality.