A lot of people shared my excitement about Philip Glass’s and Christopher Hampton’s “Appomattox,” which, after seeing a second time on Friday night, I remain convinced is a superb opera. But a lot of other people didn’t. One of my respected colleagues, as he left the theater on opening night, Tweeted to his followers that the opera was so bad people should save their money and stay home. (We can only laugh together at the disparity of our reactions.)

Even on opening night, of course, I knew there were people who weren’t as taken with it as I was. “Appomattox,” though it is firmly within operatic tradition — to a greater extent than some of Philip Glass’s other operas — is not an opera that necessarily appeals to the traditional opera-going public. If you think “Florencia en el Amazonas” is the best contemporary opera you’ve seen, you are probably not going to love “Appomattox.” I was struck right from the start that people new to opera were excited by the piece, while opera subscribers were a little taken aback.

This is exactly what I liked about it: the opera is not, like so many new operas, wrapped in a self-conscious mantel of Operatic-ness (a coinage that I mean to be just as awkward as it is). It’s direct, contemporary, and theatrical. It’s actually filled with melody and has plenty of set pieces (arias and ensembles), but it doesn’t put them in a frame by having the action grind to a halt before they’re delivered. And it demonstrably appeals to new audiences — something the opera world is always claiming it wants.

I think unfamiliarity or misunderstanding contributed to some people’s initial objections to the work, as people wrestled with processing what they’d seen. I heard that the work was simply a set of historical vignettes strung together — truer of “Eugene Onegin” than the tautly focused “Appomattox.” Others said it consisted mainly of recitative, when in fact it’s through-composed, on the model of Wagner, and has excerptable scenes a-plenty: Julia Grant’s monologue about her past with her husband, or the journalist T. Morris Chester’s painful description of the massacre at Colfax, Louisiana. Not to mention the choruses, or the achingly poignant role of Robert E. Lee, whose complicated emotions about the war and its conclusion are so beautifully depicted. On Friday, the moment when David Pittsinger’s Lee unbuckled and proffered his sword in a time-honored gesture of surrender stood out as the evening’s most moving highlight.

Some people bristled at the use of the N-word, and I think they were meant to. It’s never used gratuitously: it illustrates how people talked in 1865 and 1965, and the music gives it an extra hateful punch whenever it appears. It’s ugly, and it should be. Similarly, the epilogue, an insidious monologue of bigotry and hate delivered by Edgar Ray Killen, who arranged the killings of three civil rights workers, has a purpose. “Appomattox” depicts a few victories in the civil-rights battle, but it doesn’t want to give the impression that everything today — in the age of Ferguson and “Black Lives Matter” — is just fine; the hate, alas, is still there.

The criticism that bewildered me most was the charge that Glass’s music was repetitive and empty. On a second hearing, I found the music of Act I, in particular, even more powerful and moving than I had the first time through: music of shifting nuance, emotion, and evocative illustration, with the orchestra highlighting, supporting, and filling out the words.

Seeing “Appomattox” twice in six days was much like finishing a book, flipping back to the beginning, and starting over again at Chapter 1. Naturally, you come away with slightly different impressions. On opening night, I thought Act I was good, but a little long, and Act II was brilliant and riveting. On Friday, I had the exact opposite reaction. This may have been partly because the singers were getting a little tired; Act II seemed to have slightly less adrenaline. Opera is a living art, and offers slightly different things with each performance.

But seeing the opera again also spotlighted my one real caveat about “Appomattox.” On opening night, I was thrilled that the opera’s new second act gave voice to the African American point of view. On a second hearing, I felt it needed to do still more. The angry black chorus singing “Don’t look away, Mr. LBJ” felt powerful when I first heard it, but seemed a little shallow on the second hearing, and I felt the Martin Luther King scenes moved by too fast.

The problem, for a libretto that depends so heavily on documentary sources, is that the King estate doesn’t allow King’s speeches to be replicated on stage. Knowing this, I was forgiving on opening night of the two scenes in the opera that call on King to rise to heights of rhetorical eloquence, when he simply doesn’t. In the first scene of Act II, when King gets up to eulogize Jimmie Lee Jackson, the music and dramatic situation indicate that we are hearing something important, but all King says, and repeats, is a quote from Shakespeare: “Goodnight, sweet prince, and flights of angels sing thee to thy rest.” I initially took this as a dramatic metaphor; but revisiting it on Friday, I found it inadequate. King may actually have said this at Jackson’s funeral; regardless, I believe that if Christopher Hampton, the opera’s librettist, went in and added some better words, it would do a lot to flesh out a portrayal of King that remains over-respectful and ultimately two-dimensional.

Act II is something of an artistic tour de force. But an opera that so eloquently raises the racial issues that plague our society needs to do even more to redress them. I think “Appomattox” needs at least one other scene that gives more voice to the work’s African-American characters, even if it means tinkering with the act’s current equilibrium. Also: on opening night, when Vi Liuzzo (Melody Moore), a civil rights volunteer killed by the KKK, rose from the dead to start the final chorus of reconciliation, I found it devastatingly poignant. On Friday, I wanted to hear that line sung by a black character — perhaps Amelia Boynton, the Selma marcher sung in a strong cameo by Leah Hawkins.

So yes; I think “Appomattox” could be even better. But the fact that I am now exceeding my critical mandate by attempting to revise it myself is a sign of just how powerfully I was affected. Bottom line: I think “Appomattox” is a vitally important and magnificent new work. The Post stands by its story.