Ringworld by Larry Niven is an important work in sci-fi history. It has spawned a number of follow-up books and has influenced many other writers, heck, elements from the world Niven creates have made their way into my beloved Star Trek.
I liked many of the concepts introduced but I never found the central narrative gripping. Basically two humans and two aliens come together to investigate a mystery. I liked how the different races were handled and they came across as very different. I liked the commentary on how luck plays a part in humanity and other things like that, but I found the prose to be rather dry.
I feel like I should have liked this one more, but it doesn’t appeal to me as much as say Philip K. Dick or Isaac Asimov.