Yo.
I don't have any books though.
It probably depends on what he wants to do in Access. I think you can just write some fairly standard databases easy enough with the wizards. If he's only 14 he probably doesn't need to know how to do any fancy stuff with vba or write massively long queries.
If there's anything specific he wants help with, then feel free to ask, but I just usually tend to hunt on the internet if there's anything I need to do that I don't know how.
I do have a Business Solutions book on Excel which seemed to be ok (although I didn't read all of it), so it might be worth getting a similar book for Access. There's a 2007 version on Amazon, but it's nearly £30 which seems a bit overkill.
If he wants to know about functions, just take a look at the help files.