Rendezvous with Rama. It's all I could think while reading this book. I mean, it's a very large, strange object, which humans from Earth get inside and, while the story progresses, suddenly there are some kind of benevolent aliens, but the real monsters are the humans, in the end. And, as Rendezvous, there is a lot of over-describing stuff that is not actually important for the plot.
Sure, there are some twists, like who the aliens really are (while later in the Rama series you get why the aliens built the spaceship in the first place) and while the over-descriptions of how the aliens (in this book) look like, even if they are curious, show a lot of creativity from the author, they still are over-descriptions that add absolutely nothing to the plot.
In the end, curious, but boring.