I am looking into playing this, but if you can believe it, I know next to nothing about this 40k universe.
What is a good Codex approved introduction to this world? (video, audio, etc)
I read a few books, most were absolute dogshit, but the first Horus Heresy book was pretty good and it's a good introduction to the world. Gaunt's Ghosts was also enjoyable. Both are available as audiobooks.
For lore and quick introductions to the concepts, Luetin is like the ultimate sleep-to-this channel on YouTube entire:
I'm not that into 40K tbh but I enjoy having Luetin in the background while doing other shit
Only the first HH book is readable.
That was my point, yes.