Halo: The Rubicon Protocol
From Halopedia, the Halo wiki
Halo: The Rubicon Protocol is an upcoming Halo novel by Kelly Gay, following surviving members of the United Nations Space Command as they mount a resistance against the Banished following their ambush by them in late 2559. The novel was originally set to be released March 15, 2022, but later was delayed to April 12, 2022.
Despite having narrative connections to Halo Infinite, Halo: The Rubicon Protocol will stand on its own and will not be "required reading" for fans to understand the game's story.