J.B.
3 of my 4 daughters never had ANY interest in puzzles. That may just be what's going on here. My oldest, graduated last year, from a technical highschool, valedictorian of a class of 438 kids, a year early, with her LPN (licensend practical nurse). She didn't care about puzzles. I wouldn't worry about it.
There's always going to be that parent out there that brags about how they potty trained their kid at 18 months, and they were playing piano at 2, and reading and writing at 2.5...that kind of stuff really bothered me and made me wonder if there was something wrong with my kids. So far...they've all been well adjusted, intelligent children. I'm sure you're little sweetie is just deciding what he likes and doens't like :)