For Slaves to Darkness, as terry said, you need the General's Handbook (which is being updated sometime this month) for points costs, allegiance abilities, and artifacts. Other than that, books are optional. All the rules for the army are available either online or through the Age of Sigmar app if you have an Android or Apple device. I prefer physical media myself, so I also use the Grand Alliance: Chaos book, which also lists a few battalions for us.
|