RPG

I think every table has at least the occasional player who doesn't read or doesn't quite grasp what's written in the rulebooks. I've occasionally been that player.

I think it's worth it to talk to them specifically about the issue but don't be a hard-ass about it, this is all supposed to be for fun after all. Don't just suggest "read the book" because to some people that's basically just saying "here, read this text book" suggest the specifics parts the need to brush up on.

Maybe suggest they make, or just make one for them, a cheat sheet with the necessary info on it that they keep forgetting, depending on what they need it could just be some notes scrawled in the margins or on the back of his character sheet, or maybe a separate print-out or some flash cards.