Synopsis per the Canon Fodder article
"2559. Formerly one of the Covenant’s greatest and most fearsome warriors, Arbiter Thel ‘Vadam is now allied with his former human enemies while deeply entrenched in leading the Sangheili people to a new era of unification. But his aspirations are under constant threat, whether by the dangerous, warring factions of rival Sangheili keeps, or the relentless shadow of oppression spread by the renegade artificial intelligence Cortana.
An opportunity to break Cortana’s chains has suddenly presented itself through the rumored existence of an ancient artifact located on the hostile world of Netherop. Spartan Olympia Vale, trained with the skills to live and thrive among the Sangheili, also recognizes this alien prize as an essential means to aid humanity in reaching the same goal of freedom. But behind the scenes, both ‘Vadam and Vale are being manipulated by a mysterious figure with their own agenda. And to make matters worse, all involved are unknowingly placing themselves at perilous odds with forces beyond their comprehension."
Hopefully the book goes a bit into what’s going on with Sanghelios and the Arbiter post Halo 5. I’d like if they gave a better sense of what Cortanas plan is for the Elites and how she went about trying to pacify them. Plus, just how this whole Created Rogue Servitor thing works. How do Covenant view her. Why did she destroy Doisac but not Sanghelios. All that stuff.
Okay I am going to be very cynical here. 
It looks like it’s going to follow the trend of books Halo Bad Blood and Halo Shadows of Reach. By that I mean that although the book might briefly reference what’s going on with Cortana and the Created; the focus is going to be a quest for a Forerunner artefact in the middle of nowhere.
So here it mentions that the Arbiter and Vale are going to go to Netherop. As opposed to being on Sanghelios and doing any actual fighting there. Not promising for providing details on what’s actually going on in the galaxy.
Plus it’s putting emphasis on the mysterious forces who are going to be the antagonists of the story. Perhaps Netherop is where the homeworld of the Endless is located and they still have a presence there.
I would assume something goes wrong since we already know how Cortana was defeated and it didn’t involve Forerunner Technology.
Looks like that concept Art it was Vale talking to the Arbiter and like Shadows of Reach they outsourced some of those ideas to the novels.
It will be nice to have the Arbiter and Vale in a story again; so I’ll get it for that. But seriously, if this is what the fifth book set post Halo 5 that avoids elaborating on things in the Galaxy. You can’t say it’s spoilers for Infinite anymore.