Thanks to all for your suggestions. Bookmarked!
I choose to buy "The Revelation Space Collection" by Alastair Reynolds, based on the fact that it was suggested both here and in the reading list for "Coriolis". The first chapter already resembles an archaeological site from Stellaris! First, of course, I'll see how this "Final Days" series goes on, as it looks to be truly Stellar-ish.
Maybe I'll do a review of the books as I finish them. It would be nice to have a space to discuss books and possibly other media for fans who appreciate the lore, rather than just the number-crunching.
Oh, I almost forgot: I bought "Stars Without Numbers" too, the RPG. I still have to look at the PDF, but it looks cool.