Ringworld Engineers is the sort of book that fans of Larry Niven would have pestered him via internet had it been around at the time Ringworld came out.
It takes the original ideas of Ringworld book and expands them subtly, working it into a small but important number of the other books Larry had written previously. This is important because what fans of SF really want is for the story to make sense and fill us with wonder, in this case Ringworld Engineers certainly does that with a little hep from the other books of Known Space.
Larry Niven even managed to work in some of the issues of the day such as Racism and Drug Addiction, which were popular causes of moral panic at the time, especially of the white conservative establishment.
A worthy continuation of the Ringworld story, perhaps slightly less original than the first, but entertaining none the less.