Seventh Circle is barely an Alien novel. It's all about synthetics. The protagonist, Mae, is an especially human-like covert model that looks and acts human, bleeds red blood, feels pain, and has emotions... sort of. The other protagonist is Mae, an amnesiac girl who awakens from a cryopod that's been found by a bunch of salvagers. They have a suppporting cast of characters. Mae, Mae, and Mae. If that sounds confusing. You are right. They are all the same character... sort of. There are some other characters who are by far the BEST parts of the book, but they get much less focus and "screen time".
It's set up like a mystery with a viewpoint bouncing between two(or more) points in time. It's been done before, but the method here takes any attachments to the main character and puts it straight into the gutter. I found it nearly impossible to care about this Mae at any point in time.
Attempting a plot structure like this can get pretty messy, so you would expect the author to give you some sort of indication of which Mae and WHEN at the start of each chapter, but you generally just kinda have to figure it out for yourself. For the most part it does bounce back and forth from chapter to chapter, but that's not always the case.
I don't go into an Alien novel expecting something that's going to make my year or change the way I think about science fiction for weeks. I pick one up expecting some pulpy action horror in space. Maybe if I'm really lucky I get a bit of an eerie chilling atmospheric vibe to go with it.
Maybe that's the problem. There aren't many "real" people in the book so there isn't much character growth and there isn't much risk for it to ever be a horror novel. Even in the most tense moments, I really struggled to find any care about the characters in it.
The last 50-100 pages of this is where Xenos actually have a presence, but even then it's mostly a side note as the plot plays out. The tempo is better there, the chronological jumping about is over and we get a straight forward narrative that does a lot of work to leave you feeling like this was almost a decent book. The trouble is that it wasn't and I had to remind myself how much I hated this book all the way up until that last bit.