Helping a 23 year-old guy that can't read or write?

It's never too late to learn. The first thing to do is get him to an optometrist. I've heard there are special gles which help people with dyslexia. The next thing to do is to enrol in an adult learn to read program. Starting by reading simple Grade 1 books is great, but he may feel a little embarred. Find out what interests him then write mini stories for him to read back to you.