As he's unused to reading, try books which have very simple vocabulary, such as those written for children.
There are various websites which recommend books for dyslexic adults:
http://www.dyslexiaaction.org.uk/blo...yslexic-adults
The PDF lists are useful on that site, you can probably find ebook versions of the books.
http://www.dysbooks.com/Pages/AdultBooks.aspx
includes a section about short stories. Also if you google Short Story Websites you'll find sites which host short stories; you can copy and paste these into a text document (like Notepad) and either put this directly onto your reader or convert it in Calibre.
http://www.fluentu.com/english/blog/...ead-beginners/
This site is aimed at EFL readers, but includes suggestions which could equally well suite someone with poor reading skills. They might give you other ideas as to the type of book he may want to start with.
https://bdatech.org/what-technology/...-for-dyslexia/
This gives some ideas about which reader font to use.
Finally, it may be best if you have an ereader with a non-touch screen:
http://www.beatingdyslexia.com/eye-tracking.html
I do agree with Cinisajoy to a certain extent, so if he doesn't respond to gentle encouragement, give up and let him be a non reader.