There are 3 books in the Halo: Kilo-Five Trilogy series. The newest book is Mortal Dictata which came out in 2014.

1
Glasslands

Book cover of Glasslands
The Covenant has collapsed after a long, brutal war that saw billions slaughtered on Earth and her colonies. For the first time in decades, however, peace finally seems possible. Yet, the war is far from over: it's just gone underground. The UNSC's feared and secretive Office of Naval Intelligence recruits…
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2
The Thursday War

Book cover of The Thursday War

The second book of the Glasslands trilogy, another action packed adventure in the vast universe of the Halo game where the Human-Covenant War rages on.

Welcome to humanity's new war: silent, high stakes, and unseen. This is a life-or-death mission for ONI's black-ops team, Kilo-Five, which is tasked with preventing…

3
Mortal Dictata

Book cover of Mortal Dictata

Wars end. But hatred, guilt, and devotion can endure beyond the grave.

With the Covenant War over, the Office of Naval Intelligence faces old grievances rising again to threaten Earth. The angry, bitter colonies, still with scores to settle from the insurrection put on hold for thirty years, now want…