3.5 stars.
The book is great. Hard to read of course, brutal and terrible and profoundly discomforting, but then it's about what passed for "life" in the concentration camps. It's hardly going to be a lighthearted romp.
It's unclear how much of it is literally true. It's a memoir, and the line between truth and fiction is notoriously fuzzy in memoirs. The act of writing a memoir is inherently "fictiony"--even if every event is literally true, we also have to recognize that every choice on the part of the writer creates a narrative designed to be interpreted in a particular way. Every choice of which events to include and which to exclude, the sequence of events, the language used to describe those events-- it all creates a story. The story of Night is, sort of, about loss of faith, but one man's loss of faith is only one small component of the Holocaust, and only one small component of Elie Wiesel's experience as a victim of the Holocaust, which is far too complex to have "a story". To some extent, in a memoir the literal truth is irrelevant; it seems obvious that Night is honest, no matter whether it is (entirely or partially) true.
Example: in the original Yiddish, written in the 50s for (primarily) Jews, the liberated prisoners "rape German shiksas", but in the English translation of 2006 whose readership is primarily not Jewish, the liberated prisoners "have sex with girls." There's a lot to unpack from just a few words--the motivation behind rape (a crime of power, violence, and/or revenge) vs. sex (an act of unity and humanity), "German shiksas" (which emphasizes an "us vs. them" mentality) vs. "girls" (which eliminates the divisive language, but doesn't change the fact that the only available women would have been German shiksas). The choice of phrasing was deliberate in both instances, and it tells us a lot about how Wiesel wants different audiences to interpret his book, or at the very least how Wiesel's intent has changed over time. It's a useful reminder not to blindly accept as fact every word of a memoir, even if as a whole, it is an honest representation of a period of someone's life.
Why (only) 3.5 stars, considering the abundance of 5 star reviews here at goodreads (all my friends who've read it have rated it as 5)? Frankly, as moving as it is, I have found a handful of other books about the holocaust (fiction and nonfiction, both) to be more so. This is partly due to the length--it's so short that I'd hardly had a chance to get invested in the characters before it was over. And it's partly due to the story he chose to tell, about loss of faith; as an areligious person, I'm simply not very interested in stories about spirituality. I get the impression that a less-than-perfect rating where this book is concerned is controversial, but the book is not exclusively an artifact of the holocaust. It's also a memoir--deliberately a memoir, not an "autobiography" or "non-fiction account" or "reportage" etc. -- and consequently has an obligation to its readers to be a story worth reading. In that regard I get to judge it on its quality as a book, rather than its quality as reportage or historical artifact. As a book, in my opinion, it is great but not phenomenal. So, 3.5 stars.
I have to admit that separating my feelings about the book from my feelings about Elie Wiesel was difficult. Of course I am in awe of every person who survived the concentration camps (although that raises its own set of ethical questions: how am I supposed to feel about the bad people who survived the camps -- the rapists, the child molesters, etc.?). And I am in awe of Wiesel's choice to become a spokesman for the oppressed, a choice that has forced him to relive his experience every day when it would have been easier to choose to live a small quiet life and move on (as much as that's possible). But I simply don't agree with his positions on Israel, Jerusalem, Palestine, and the "uniqueness" of the Holocaust, and I think he has become an enemy of the Jewish people. Because of his fame, his voice is loud and more influential than it deserves to be. Why does this matter? Because Night isn't just Night; it's Night and Elie Wiesel and all the baggage that comes with that. That's a pretty heavy burden for a book this small.