Board Thread:Young Justice News/@comment-3974095-20170209201908/@comment-3974095-20180515174007

Recommended reading :
 * Batman & the Outsiders Vol 1. (1983) — (collects #1-3, The Brave and The Bold #200, and New Teen Titans #37): Batman must abandon his old allies and form a new force for justice—a team of heroes who aren’t afraid to operate outside the rules. Features Katana, Black Lightning, Metamorpho, Geo-Force, and Halo.
 * Amazon
 * Barnes & Noble
 * Outsiders Vol 1. (2003) — (Collects #1-7): Arsenal recruits a new team, with Nightwing as leader. Team consists of: Nightwing, Shift, Indigo, Grace Choi, Thunder, and Arsenal himself.
 * Barnes & Noble

I'll update this list periodically. In the meantime, these books are both great places to start, especially the second one which appears to be the basis for season 3.