These books are part of a larger series, though neither is labeled as such.Revelation Space is an interesting and compelling story. It is one of the few sci-fi books that I've read where travel faster than lightspeed is not possible. In fact, travel at lightspeed itself is not possible. As such, while characters move between worlds, hundreds of years may pass. This has an interesting effect on galactic travel and politics. While there are hints that travel faster than lightspeed is possible, no one really has the slightest clue how to get it done. I won't reveal the book's plot here, but I will say that at times, it can double back on itself in some very interesting ways.Redemption Ark is follows in the footsteps of Revelation Space, but there are some new characters introduced and some new plotlines explored. At then end of the book, it is clear that yet another tome will be following these.
If you're looking for some relatively long, well considered science fiction, I would recommend both of these books.