If you want to wet your whistle, I recommend watching Astartes 1-5 on YouTube. Captures the feel for the 40k universe quite well.
As far as reading, Dan Abnett is my favorite 40k author by far. He’s responsible for Gaunts ghosts and eisenhorn (among others).
If you want to fall down a deep DEEP rabbit hole go check out
https://warhammer40k.fandom.com/wiki/Warhammer_40k_Wiki
Just be careful, you can get lost for hours here.
Old Man’s War is actually pretty good by itself. The rest of the series falls off substantially after that.
The problem with Scalzi is that he is almost entirely dialogue driven. He can’t describe a setting to save his life.
Women think they want girl superheroes but then they don’t watch it. They want girl action and sci fi heroes but then they don’t watch it. They want their basketball stars to excel but don’t watch the WNBA.
But the Barbie movie comes out and they see it in droves.
I’d draw a similar parallel to Sarah Connor in T2. She toughened up and went all female Rambo not because she was trying to out man the men but because she devoted her life to a singular purpose: Keeping her son safe and preparing him for the future.
The only black authors I’ve seen are economists like Sowell or political commentators like Williams or Elder.
I don’t know a single fiction writer who is black.