Invictus is not your typical space opera or military sci-fi. Though it has elements of both, it is a much more character-centric story, with a plot that in some ways is incredibly simple (at least in book one), but works due to the need to slowly figure out what is going on amongst all the secrets being kept. 

This is a culture clash of two very different civilisations, with a lot of worldbuilding established (there are some useful reference materials at the back of the book). One of these civilisations are comprised essentially of genetically engineered cyborg clones (though I don't believe those words are used in the novel), while the other civilisation is descended from those who originally created and enslaved them. 

At the centre of the book is the interactions between the characters from either side, who don't know whether to trust each other but still come to care about each other. Sevastien is a compelling main character and the emotional moments in the story come from his experiences being held captive and cut off from his people. 

It's probably not a book for everyone, but I found it usual and intriguing, and I will be reading the second book in this duology.