So the vampire bit is used in both, in book 1 the main character journeys with one and at the end of the story starts to think Earth has been taken over by vampires due to radio transmissions he’s receiving on his long voyage back home. Book 2 begins with a prologue of a group of vampires breaking out of their holding cells, reversing the Crucifix Glitch on their captors, and then their leader eventually groups up with the main character (as well as the dad of book 1’s MC) and they all journey to the Sun (or rather, a station orbiting the sun). The second book also has that group/cult of people who are trying to make a gestalt consciousness, the Bicamurals I think they’re called.

Like ai told another commenter, I don’t like it as much as Blindsight, but I still think Echopraxia is really good, they just focus on wildly different topics.