The tragedy of our education system is that it is too exam oriented and attempts to make all of us academics oblivious to our individual talents and preferences, which is a pity really.
Perhaps the right place for you to begin would be to ask yourself, besides reading, what else did he participate in while in school- games? Any extra-curricular activities? Therein might be a clue as to what his talents and/or interests really are.
While at it by the way, what has he told you that he himself would like to do? If he's just recently finished his high school, give him a maximum of about 7 months post high school after which he should have decided what he wants to do; it took me about 6months after high school before deciding I ever wanted to see a book again.
Maybe as he goes about making up his mind, you might wanna consider some form of apprenticeship for him in a variety of fields. I see young men at my pal's garage doing that all the time, just to keep themselves busy.
Life is like playing a violin solo in public and learning the instrument as one goes on.