The Superlative Stream is the second book book by Kerry Nietz in the Dark Trench sci-fi series.
From the "back of the book":
"He crossed the stars to follow a song...
So where's the singer?
Sandfly is free of the rules and free of Earth, but now there's a new mystery to solve.
With his female companion, HardCandy, and a secret ship named DarkTrench, he travels across time and space to find the source and meaning of the transmission that changed his life.
When they arrive in the Betelgeuse system, they discover something the former crew did not--a planet. On it lives a civilization of humanoids that are technologically advanced, peaceful, and mystifying. Is their meeting an occurrence the Scriptures predicted? HardCandy thinks so. Sandfly is not so sure.
But what he most wants to know is why is he seeing things no one else can.
And where is the song that brought them here--or its singer? Where is the Superlative Stream?"
Sandfly, Hard Candy, and Dark Trench are back from book one. New characters are some of the aliens that go by "Ham", "Shem", and "Japeth" (there are actually lots of the aliens, but these are the main ones we interact with.)
This book is a lot more "literary" than the first, by which I mean there's a lot more inner dialogue, more character struggles than just external plotting.
Not that there isn't a plot, there is, and it's quite intriguing and immersive, it just takes a while to get to it. Most of the first half of the book is Sandfly wondering where the Superlative Stream they came to find is, and him growing in faith and stuff.
Still, it's a solid middle of the series book. Like most middle books, I'd recommend getting this and the next one (Freeheads) and reading them back-to-back, but the book still stands on it's own well enough--a refreshing change in modern series fiction.