This is a novel about the first contact between the human race and an alien species by Larry Niven and Jerry Pournelle. Humanity is technologically advanced, occupying many planets and having faster than light interstellar travel. The aliens are more advanced than us in many respects, but do not have ftl travel.
In addition to being a very readable novel (along with its sequel) it is also a very well thought out first contact. It is much better than either the books where we defeat aliens by attacking them with fighters or the books where aliens must be open to friendship and cooperation and similar to us. Understanding the aliens is the key to survival and prosperity in this novel, as it will most likely be if we ever meet any actual aliens. This book is a good candidate for the thousandth thousand club.
Somewhat less credible is the benevolent imperial government complete with lords and ladies, which seems to be a cross between imperial Rome and medieval England. It still gives readers much to think about as well though.