This is an odd one. The writing is enchanting, and I don't mind Nick, but the other characters are very nasty.
Gatsby himself is depressing. He didn't ask the girl who he thought he loved to marry her while he had her, and when she got tired of waiting for him, he was unwilling to give up his dream of being with her. He stalks her until he can manipulate her into starting an affair with him, but pushes too hard and doesn't take her seriously when, in the confrontation scene between Gatsby and Tom, she admits that she did, in fact, used to love Tom. He is so hung on his dream of being with her, that he refuses to consider the fact that she might not want to be with him. And in his years of dreaming of her, he built up his memory of her to the point that it depicted a goddess, rather than a woman. He was undoubtedly disappointed with her once he had her, but he was so attached to his dream that he wasn't ready to give her up yet.
Daisy is annoying. She is, sadly, trapped in a loveless marriage. She had loved him before, but their love faded with time and her husband had been cheating on her, and she was aware of it. As sad as that is, it seemed like she was getting by, by clinging to her friends and to her daughter, but when Gatsby came back into her life, she decided she was willing to have an affair, but, when he pushed her too hard, insisting on her behalf that she was leaving Tom and that she never loved him, she decided (understandably) that she wouldn't find joy in him either. But she was willing to let him take the blame for her vehicular homicide, and she was so indifferent that she didn't even call, much less come, when Gatsby was killed.
Tom is obnoxious. He thinks he is entitled to his wife and a mistress. He can't understand why his wife might no longer love him, nor can he understand why his mistress's husband might not like his wife gallivanting off with another man. He is stupid and loud.
Jordan Baker is shallow. She lies, probably cheats, and doesn't mean a thing she says. She starts an affair with Nick, but then is shocked when he eventually splits with her, even though it is implied that she had been considering splitting with him. As though she is too good for anyone to break up with.
Nick is a strange narrator. For some reason he comes to like and respect Gatsby. While I admire his loyalty, I don't know what he saw in Gatsby to make him so loyal. He doesn't seem to have a problem with Gatsby and Daisy having an affair, though he's discomforted by Tom's affair. He had a fling with Jordan Baker, even though he knows she's a liar.
There are some nasty stereotypes of Jews in this book. Worse even than Fagin in Oliver Twist. Fagin may have been presented more as a villain, but you could understand how he got to be so low in the world and so despicable, but Wolfshiem is a stereotype without any understandable reason for how he came to be how he was. I'm not sure how Jews feel about the term "Jewess," but I've only ever heard it used by Nazis, so I was discomforted by the casual use in this book.
I heard this book described as being a depiction of the time between World War I and the Great Depression when too many people had too much money and too much time on their hands. And apparently not enough morals. It certainly depicts that well.