Almost all of the background for the Infinity Universe is found in the Core books that are sold as part of the Infinity N3 Rule book and the Human Sphere N3 Rule Book. The latter is a more complete text. The other official sources are the Campaign Paradiso book, the Uprising book (May 2018) and the Outrage graphic novel.
There are also a number of talented writers in the community who write fan fiction, and the following is a list of their known work – please contact with any omissions, thank you.
DaRedOne – Stories About Angry Monkey Men
The Wrecking Belles by Danger Rose