Ringworld is one of the most classic of science fiction classics, and yet often the fantastic setting(which is one of the best in science fiction history) overshadows the other ideas that are going on. One of the most overshadowed are the kzin, who take a back seat in the story of ringworld even though there is a kzinti with them.
In the anthology "The Man-Kzin Wars" the Kzin step forward, and while we still get to see fascinating places and visit worlds that are both brilliant in their scientific understanding and storytelling importance it is the kzin who become the most interesting aspect.
The Kzin are a race of cat people, and from that you might assume that they are like any number of cat races in science fiction. If they are it is because those races took the ideas of Larry Niven and used them. This is a race of carnivores who believe in strength above all else. They have spent centuries breeding their women into what amounts to little more than pets and whenever they aren't at war they are preparing for it.
With this understanding you might assume that the kzin are little more than moustache twirling villains but they are far more than that. This is a race that in many ways is more honorable than humans are. They won't, or can't lie, they will almost always fight fair, and if you prove you are truly stronger than them they will submit and become quite loyal. In many ways it is this honor that allows them to continue to fight wars where humans, who don't follow any of those rules can't afford to because they would annihilate themselves.
There are three stories in this anthology, the first by Larry Niven himself covers the first meeting between humans and kzin. The humans after three hundred years of peace are hardly able to understand what is happening when the Kzin attack, but once they realize it they fight back with an efficiency the kzin can hardly understand.
Next is a story by Poul Anderson. This is the bulk of the book, taking place after the first two kzin wars, the Kzin have discovered hyperspace and with that they will soon be on equal footing again to fight humanity.
The third story begins when the kzin attack. The only survivor is captured by the kzin and put on a zoo world where he discovers kzin women from before they were bred to be docile and stupid and we discover why they were so dangerous that the Kzin men chose this course of action.