I would highly recommend the works of Katherine Paterson. One of the best known is The Bridge to Terabithia, a moving story of being different, a friendship, and death. However all of her books (at least all that I have read) are marvelous, and often incorporate themes that could lead to a good discussion.
Although often somewhat sanitized when written for a younger reader, biographies are also a great way to lead into discussions–Jackie Robinson, Rosa Parks, Jesse Owens, Eleanor of Aquitaine, Susan B. Anthony, Sojouner Truth, Elizabeth Cady Stanton, Clarence Darrow, Cesar Chavez, Joe Hill–the list is endless.
Another source for discussion starters would be looking at the mythology and folk tales of various cultures. I don’t have a name off the top of my head, but I remember one book (may be a lower reading level) that had several creation myths in it. There are any number of fine books re-telling the major myths of different cultures, though, so if it interested the two of you, you shouldn’t have problems finding them.
And just for fun, if he likes fantasy, the David Eddings books (esp. The Belgarion) are suitable for his age level. The basic “journey to discover who you are” story, it has some fighting, but nothing too gory, a little romance, and enough action to move the story along without sacrificing character development. Not as good a Lloyd Alexander (but similar to the Book of Three series), or Susan Cooper, but much better written than anything by Terry Brooks.