On balance, I do like Ringworld, or at least the concept of the ringworld. The idea is that a forgotten race of wildly talented engineers have built a complete ring around a star and outfitted it with gravity, atmosphere, vegetation, animals, and even sentient life. The scale is so vast that it's nearly impossible to comprehend. (The ring, Niven tells us, has the surface area of roughly three million earths. There are mountains thousands of miles high.) I give Niven a lot of credit for the thought he's put into his concept. It seemed, to me, that he had thought through nearly every implication of the ring, what it would require to work as he needs it to, and how it would look. It makes the concept strangely believable, even as it's difficult to envision (again, the sheer scale of the thing gets in the way) and very, very memorable.
The plot, on the other hand, was somewhat weak. Really, the book is just a sightseeing tour of the ringworld. And that's fine, because the ring on its own is fascinating enough to carry my interest. But not enough to get me well and truly invested so that I want to read on with other books set in this universe.
I have a quibble about the characters, too. Not the male characters, as Niven did a fine enough job fleshing them out and making them living parts of the book, regardless of species. The female characters, on the other hand... They're shallow, shells of characters compared to the males. Teela is on the mission to sleep with the main character and because she might be a good luck charm. That's it. She has no useful skills to contribute, nor is she asked to. Sleeping with Louis is enough. And her personality is exactly as bland, shallow, and borderline dim as you'd expect, given that description. Her bland personality might be partly explained by her supernatural luck running interference and protecting her from all harms. But wouldn't it also be lucky for her to be skilled in exactly the ways that would be useful for the mission? Seemingly not. The only other woman in the book, Prill, is met on the ringworld. Her ship crash-landed on the ring long ago. And as a woman on a ship full of men, obviously she must have been the ship's prostitute, right? I mean, why else would there be a woman on board? Logic that's fully accepted, never questioned, and is ultimately proved absolutely correct. Yes, this doesn't take me by surprise in a book written in the 70s. But it's still irritating.
As a concept, Ringworld is one of the greats. The execution is lacking in plot and, especially, female characters. While I like the idea, the casual sexism left a bad taste in my mouth.