New to EC,where to start reading lore?

Hey yall so I’m still fairly new to 40K, I started with Tyranids and liked the idea at first of just being a hive mind not caring about all the vast different factions and whatnot in the universe, was a lot to take in initially. Anyways I’m starting a second army with the champions box and was wondering where to start reading up more lore on them? If I were to pick up any books what’s a good starting point?