When my niece & nephews hit a certain age, I gave them cash/gift cards. I was interesting that my niece was thrifty and saved her money, while her brother would have spent the money before the end of the day online buying more computer gaming stuff. Anyway, cash & gift cards are fine from an uncle, but I bet you want to give him something more personal than that. I was gonna say some type of electronics kit, but I don't really know him. Does he drive yet? Does he have a car? A nice detail job might be a fun thing to give him. Skimming the web, I came up with: Link It's a moon lamp. Link Lens kit for certain cell phones (you'll have to search to find the one for his phone) Link Personalized wallet (monogram, his name, etc) You could even put something in it. Link
@John Brunner I like the book idea. He is always asking me questions about stuff and we get into some really deep conversations. There were several others that I think he would sit down and actually read. Thanks.
When my son was with me, I had a pretty good idea as to what he would want because he'd make sure of that. The grandchildren are another thing. I am not with them often, and, while I was only thirteen years older than my (adopted) son, I'm more than fifty years apart from my grandchildren.