Pushing Ice by Alastair Reynolds
Here's another book that has some hints of Rendezvous With Rama. The book's prologue does start on a different note - looking back from 18,000 years in the future when humans have an interstellar civilization. But after the prologue we have the familiar premise of a large alien artifact going through the solar system. Human activity in space is already at the stage of "pushing ice" - mining comets. As in Rama, there is only one human spaceship that is capable of intercepting the alien ship long enough to explore it for a short period of time, then returning home while the alien craft goes away.
There are, of course, differences. In Pushing Ice, the alien ship had been disguised as Saturn's moon Janus prior to leaving orbit and heading for the stars. Also, a substantial beginning part of the book deals with crises the human ship faces in deciding to head on an intercept course and during its trip to catch up with Janus.
We're about 1/3 of the way through the book by the time humans start exploring Janus - and even then it's not so much research on alien artifacts as it is an effort to see how humans can find a way to use Janus to prolong their survival. By this time the humans are essentially castaways stranded on Janus as it travels to another star system.
Conflict has begun by this time between the captain of the human spaceship and a top engineer in the crew. As in the Rama sequels, conflict between human factions is an important part of the plot. It will interest some readers that both of these two opposing leaders are women.
At a certain point, after humans are well-established on the alien vessel, Janus surrounds itself with an opaque shell which is impenetrable to humans. Later, a hole appears in the shell and the humans find Janus is now parked in a vast structure and there are aliens there. Humans are faced with questions of what to believe about which aliens.
At first, that isn't so complicated. There is one alien race that shows little sign of acting against humans. On the other hand, while they do provide humans with some new technology, they provide it at a frustratingly slow rate. And the technology they provide is from a human society which the aliens are rather vague about. After a while these aliens warn that another alien race, which they describe as dangerous, will be coming before long. When the other aliens arrive, they present themselves as being friendly and more generous than the other group. Who do you believe?
This puzzle is complicated by the human's factional conflict. The two alien species are different. Readers who like various kinds of aliens may like this aspect, although I don't think any new ground has been broken here. As far as what the reader is clearly told, we never meet the builders of Janus or the vast structures it goes to. We do see some futuristic alien tech, but we only learn a little about it. So what the book has to offer to you will depend on what you're looking for.
I felt it had more to offer than the Rama sequels. There was too much human factionalism and too little learning about alien tech and aliens for my taste (considering it begins as an “alien artifact” story). It has that in common with the Rama sequels. Yet, for me, it was not as disappointing as the Rama sequels..