There are 3 books in the Halo: Ferrets series. The newest book is Divine Wind which came out in 2021.

1
Last Light

Book cover of Last Light
It is 2553, and the three-decade-long Covenant War that defined a generation has suddenly drawn to a close. Yet in the remotest parts of human space, tensions remain that threaten to overflow into another full-scale conflict. Beneath the surface of the planet Gao lies a vast cavern system renowned for…
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2
Retribution

Book cover of Retribution
December 2553. Less than a year after the end of the Covenant War, a string of violent incidents continues to threaten the tenuous peace in human-held space ... culminating in the assassination of UNSC fleet admiral Graselyn Tuwa and the abduction of her family. It is a provocation so outrageous…

3
Divine Wind

Book cover of Divine Wind
An original novel set in the Halo universe—based on the New York Times bestselling video game series!

October 2559. With the galaxy in the suffocating grip of a renegade artificial intelligence, another perilous threat has quietly emerged in the shadows: the Keepers of the One Freedom, a fanatical and merciless…