If you can get him to read the first one he'll be hooked. I loved that series as a kid. Another favorite of mine was Alfred Hitchcock and the Three Investigators. What kid wouldn't want to be part of a team of private investigators who made their headquarters in an old trailer in the midst of a salvage yard?
The Hardys and Nancy Drew are still in print, but I haven't seen a copy of the Three Investigators in years.
I've never even heard of the Three Investigators! LOL
He's never at a loss for books. Reads on a lot of different topics. But, I agree that he'd probably like them. Oh well, perhaps in time. He's into ancient civilizations at the moment.