Hard science fiction but focused primarily around three characters, so the science is more of a background than the primary focus. On a future colony world that will be settled by Earth descendents, daylight and night are so extreme that the full light of day literally sets crops on fire. Cities have to be carefully shuttered and crops shaded in order to survive. The world is clearly at least several generations post-settlement and much of their ancestors' original equipment is breaking down, while weather changes to the planet cause additional problems.

In between the strictly regimented city Xiosphant and the criminal-controlled city Argel, the plot follows a pair of friends, Sophie and Bianca, and a smuggler, Mouth. Sophie tells her part of the story in first person, so is clearly the 'main' character, and when she is thrown out of Xiosphant into the Night to die, she discovers that one of the native alien races (the "crocodiles") are actually sapient. If there is a fourth main character in the book, it's the crocodiles; through Sophie, they try to communicate with the humans to explain that human actions are what's destroying the planet and causing the devastating weather changes, as well as causing huge suffering and death to the crocodile population.

Sophie, however, is both powerless and rather easily distracted, mainly by Bianca, who she adores for reasons that become less and less easy to sympathize with. Bianca, a privileged rich girl from the upper class section of Xiosphant, initially appears to be a good friend to Sophie but through the course of the book becomes more and more selfish and closed-minded, to the point it rapidly becomes very frustrating watching Sophie continue to trust and follow her.

Mouth is probably the most interesting character in the book. Initially she's fairly unlikeable, but as you learn more about her background and what she's suffered, and as she grows to be a better character, she becomes more and more sympathetic.

Ultimately Sophie, with the help of Mouth, attempt to initiate communication between the crocodiles and the human settlers. And at this point, the book ends very abruptly, without a satisfactory conclusion or a clear indication of what the outcome will be.

Overall, the book was very interesting; I really liked the alien world; the crocodiles were a great species; the society and politics were interesting; and the book was well written. However, the ending was a let down and felt as if it cut short several chapters too soon. I am guessing there's a sequel planned? But I'm not a fan of leaving a book unsatisfactorily short, even if it does have a sequel coming.