A year or so ago I finished Morgan's Broken Angels and Woken Furies, which are the last two books of the Takashi Kovacs trilogy. They deal with a few mysteries surrounding space artifacts and forgotten interstellar cultures, and these mysteries frame the larger explorations of the worlds and cultures the author has created. The whole trilogy is pretty good hardcore, action scifi. Morgan clearly enjoys writing characters within military/corporate hierarchies and the dynamics and attitudes that come out of that. That may be a turn-off, I was a little tired of it after the last book.
(By the way, Morgan's "sleeve" technology is really well handled, it allows for very interesting twists on story telling conventions. It's one of my favorite technologies in any scifi, it's very slick yet doesn't get bogged down in detail.)
Another fun but much goofier exploration of a world and artifact is John Varley's Titan. It's just straight-up weird, the creatures and the world itself. Don't get me wrong, I'm not saying Titan is a good book. It's part of the reason scifi and fantasy fans get stigmatized, it can be embarrassing in places. But it's fun, dammit. So what if it's trashy and *very* dated? In its defense, the protagonist isn't half bad, it's just hard to be taken seriously in the world Varley creates.
Titan especially is easy to get through, it goes fast. Broken Angels and Woken Furies have some bloat to them, but Morgan's technologies and politics make the ride interesting. If you read one of them, hope you'll discuss them here!