Well, I haven’t read Age of Fable but I glanced through it. I have read Tanglewood Tales (and A Wonder Book, which comes before TT). Age of Fable covers many more stories than TT from the looks of it.
However, my sincere and hearty recommendation is to read both the Nathanial Hawthorne books starting with A Wonder Book and ending with Tanglewood Tales (both are audio books as well). They are wonderful and told in a great story format. Compared to them, Age of Fable seems kind of dry and overly long (like I said though, I haven’t read it).
Yes, they are appropriate for him. =) It is stories about the heroes and legends of Ancient Greece – but the setting is what makes them special. It is a group of cousins meeting for holidays at the grandparents house and the oldest is in college. They have adventures and while they are resting during the adventures, they beg him to tell stories. So he does, and he has a great ability to share these stories in appropriate ways. I really enjoyed his version of King Midas.