You're right Ultramorph. I just caught that with a simple bit of Googling... I'm 3 chapters in. Well it looks so far like they're really trying to explain a lot and stay consistent with "canon" in that case. I am really enjoying the book so far.
Here's a little bit about the name of the book for those who haven't guessed it:
Spoiler
Acheron comes from the ancient Greek mythological "River of Pain" which wound through the netherworld. This is confirmed in the book.
Four chapters in and I'm really enjoying it. The author is really focusing on character development rather than like the characters in Sea of Sorrows.
I'm listening to the new (ehem very old) Pink Floyd album while reading. "Endless River". No, the irony is not lost on me. It's a cool way to enjoy the book. No singing means no distractions yet a pretty cool vibe...
Here is the back of the book...