I really should have read this when I was younger. Still, better late than never.
Anyway, the novel is about the discovery of an anomalous object in orbit around Saturn by a deep space expedition. Cirocco Jones captains the expedition as they, and Earth, realize that its a first contact situation. From there, things turn into an adventure (adventure being defined as being in deep trouble far from home).
The world building is neat and Cirocco is very much a 70's to 80's character, but I like her - she's interesting and abrasive.
Cross John Carter of Mars with a sentient scaled-down Ringworld and you get John Varley's Titan. Frankly, I like the Titan series much better than the Ringworld series. Varley doesn't get sidetracked with inter-species sex to the extent that Niven does. And the smaller size makes the story fit better to the surroundings.
There are two more books in the series, but you can read this one as a standalone. (Although I recommend reading all three.)
This book is good science fiction with an adventure story that is easy to follow and keeps you going. A group of astronauts on a mission to study moons of Jupiter discover an artificial world orbiting in an eccentric path. When their ship is grabbed and dragged inside the huge artifact, being destroyed in the process, the astronauts are separated and changed by the intelligence that governs the artificial world. Aside from seeking out the scattered members of their original crew - each of whom has undergone some fundamental change to their psyche and/or physical being,the main story centers around the various species they encounter and the trek to the core. The species include centaurs who are at war with a species of flying humans who look like angels, kilometers long hydrogen lifted aware blimps, and several others. Overall I would say it reminds me mostly Larry Niven's original Ringworld with some elements of Jack Chalker's Well World thrown in for good measure. Given the premise of the wheel shaped artificial world populated by various species and cultures and the adventure built around the trek to the "core" to discover who runs or built the place it is definitely very similar to Ringworld. That's not a bad thing, just an observation. On it's own I rate this book as definitely worth reading.