Everyone on Cocytus immediately wanted to go into Space Time Six so they would no longer have to face death and so they could go into a state where they fealt great, but as it turned out immortality turned out to be a living hell.
I haven't read the novel, but I believe it'll be just as you are saying: It has much more details and plot elements than those the game has, and expands on the characters as well.
It was interesting to see what lead to the 'destruction' of the Cocytan race: The desire for inmortality. The Creator had this in mind, but seeking to benefit his race at the end. He didn't realize the consecuences of this until it was too late. Initially, nobody cared if they had to live a life of 'self-slavery', they only wanted to escape death. And then again, they changed their minds a bit too late... As a matter of fact, Brink himself admited that life through the crystals wasn't worth it. He only wanted more and more of them, no matter the cost.
This shows us that it's better to have a short but 'rich' life, than an infinte but pointless one. Going out with friends, getting in love with someone, practicing sports, getting a job I like... I wouldn't trade any of that for being something close to 'inmortal'.