Available now; grabbed the eBook off iTunes and read it in between tours at work.
Feelings haven't quite gelled overall on it. I loved Peter David, based on my exposure to him primarily through the excellent Star Trek: New Frontier books, aka expanded universe Star Trek novels that carried forward the universe and didn't suck, a comparative rarity at the time they came out.
There's definitely a bit of Star Trek influence in his writing here (the Halo universe has antimatter?) But ultimately I'm not sure if he nails the central dynamic this book is designed to highlight—humans and Elites, working together, in a tenuous relationship. We get the Spartan who wants to kill the Elite, we get the Elites who (quite rightly) aren't going to let UNSC politics hold them back, and we get some little touches and bridges between Elites and humans in Vale, who we'll presumably be seeing be useful on Sanghelios in Halo 5. But much like Mortal Dictata, I felt like this book just sort of ended, without any sort of big crescendo or denouement. The central crisis is resolved... but I didn't feel like we got any sort of real ending or understanding for most of the characters. Part of the problem was there were apparently five more than we actually needed in this one; it feels like David realized his halfway in because he breaks on of their legs and sends some of the dead weight characters home to disappear until the end of the book.
The Elites never really felt like Elites, to me—Traviss did a much better job with them overall, although ironically enough for every "as the humans say" in her books we got a "The Elites have a saying" in this one.
I did think the book did some nice rumination on the differences between the Spartan IIs and IVs, and how those differences could alternatively be a liability or a boon.