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 releases in March 15, 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.