If I did decimals, this would be more a 3.5/5, but alas, I don't, so suck it.
Snark aside, as the title suggests, this is the actual story 'The Little Mermaid,' as written by Hans Chrstian Andersen way back in the day. As mentioned elsewhere, one of my writing projects is a Little Mermaid story, so thought it best to go back to the source. Worth of that endeavour aside, how does this hold up as a work of fiction by itself?
Honestly, reasonably decently. I'm going to assume that you haven't read the book, and are generally unfamiliar with the archtype of the tale (tail?), which is unlikely, I know, but regardless, seems to be the best way to go about it.
Under the sea, there live the mer-folk. Six daughters of the King of the Sea are allowed to go to the surface when they turn 16. Each daughter goes up and is entranced by the surface world, but soon lose interest, and find that life under the sea is much better. This, however, puts a sense of longing into the titular character (I should note that no-one is actually named in this story - the Little Mermaid is just called "The Little Mermaid," for instance), as her sisters keep coming back with these wondrous stories, so it's all the sweeter when she finally makes it to the surface. Sweeter still when she sees a hunky prince and saves him, singing to him on the beach before returning to the ocean.
Lots of time passes and the Little Mermaid remains besotted with the prince. She keeps returning to the surface and hears gossip about him, glad to hear that he seems like a decent fellow, and secretly pleased that she's the one responsible for saving him, even if no-one knows it. Alas, being a horrible abomination of fish and human makes things a mite difficult. Her mother/grandmother (not sure which) cautions her against such feelings, and explains the differences between humans and mermaids. Humans are mortal, but have souls, which are released upon death and go to Heaven (not said in those exact words, but that's the gist of it - the book's very Christian in its outlook). Mermaids, on the other hand, live up to 300 years, but have no life beyond death, and upon death, turn to foam and become one with the sea. To the LM's mother, this is a good deal, but not so much the LM herself. Eventually, she sees the Sea Witch and makes a deal - the Sea Witch will take her voice, and in exchange, make her human. If she can get the prince to fall in love with her, she gets her happy ending. If the prince takes wife, however, she will return to the sea (as in, die, become foam, etc.)
The LM takes the deal and meets the prince, but with her being mute, communication is a downer. The prince is clearly fond of her, but nor does he seem to truly love her, and marriage isn't happening anytime soon. Her sisters greet her from the sea, but she can't go back. Eventually, the prince takes a wife from some other kingdom and marries her, which means that the LM has until the next sunrise. Upon the prince's ship, as he sleeps with his wife, her sisters offer a knife and a way out. If she kills him before sunrise, she can return to her life as a mermaid (there's a bit more detail as to how this works). However, as she truly loves him, she refuses to take his life. As a reward, upon death, she's greeted by beings that I thought were angels, but are apparently air elementals. Apparently moved by her moral centre, she can join them in bringing joy to people, and one day, ascending to Heaven, as she's earnt a soul.
I'm not 100% sold on the ending. Really, the book can be described as a tragedy (in the literary sense), but the creatures offer the LM an 'out,' rather than her having to face the full consequences of her actions. On the other hand, her love remains unrequited, through no fault of the prince himself, and she pays the price (in a sense) for her actions. But that aside, the book is decent. It flows very well and the writing is perfectly readable, despite having been written in the 19th century. The Christian theology may be a take it or leave it aspect, but for me, it's fine.