*EDIT* I've added another star, because although this book was not extraordinary by anyone's standards, I enjoyed it quite a lot. 
 Nightfall is OK, as long as you're not expecting an enlightening read. It's undeniably fast-paced and entertaining, but I probably wouldn't read a sequel if there is one thanks to the characters. They're not annoying or even that unlikeable, but just really bland. The only one I cared about was Kana, and he had some pretty good character development (view spoiler)[ especially as he starts to turn into some sort or humanoid-reptilian creature (hide spoiler)]. 
 The story is as exciting as it promises to be, but all in all is not much more than a better-than-average pulp fiction novel. That being said, I certainly don't regret reading it, sometimes it's nice to just enjoy a easy to read sci-fi.