I think the implication is that you do not need to read them to be afflicted by there presence i dont think any of the characters are sitting down and reading the grims in the middle of a mission !

Magic book make Ogryn feel funny

I am amazed how some ogryn players are even able to read...because sometimes i have the feeling that a rl ogryn sits behind the screen at home playing himself.

Originally posted by Ephringael:

Magic book make Ogryn feel funny

Is that why the Ogryn is able to fix computers faster than two veterans and a zealot?

Nurgle Grimoires are all picture books. No words needed.

Sometime during leveling there is a cutscene with runes of Nurgle inside a room, several guardsmen throw up just from seeing them, they can't read them, they don't understand them, it's just tainted and just being nearby causes those weak of will to get shaken.

Understanding what you see is even worse actually, kind of like insanity in Call of Cthulu, those blissfully unaware just become alcoholics, those who understand things end up bats**t insane.

I've heard characters in game refer to the Ogryns having undergone the BONE treatment.
Having the Bonehead implant.
That puts them on the level of average human adults.

So yes, reading should be no problem for them.