The first book in a trilogy by Alan Dean Foster (first print in 1974). Alternatively also the name of said trilogy as a whole.

The story is about a group of people crash-landing on Tran-Ky-Ky, a frozen world inhabited by the Tran, a quite intelligent, feline people. They manage to survive first contact and develop a kind of friendship with their hosts.

It's also about how to make a medieval culture familiar with concepts like plasma forges, gunpowder or hovercrafts and the possible future shock that might be the result. It's about exploitation of a less-developed people and many more ethic pitfalls, all that packaged into one of the best stories I've read so far.

The books in the trilogy are:

Sadly it seems that the books are out of print, but if you can get at them and like good SciFi, I would recommend you have a look.