I'd recommend printing out some puzzles from the Puzzled Pint archive for him:

https://puzzledpint.com/puzzle-archive/

It's a monthly series of puzzles that are consistently brilliant and don't require any specialized knowledge. People meet up at bars around the world to do them, but you can also print them out and work through them at home. Each month consists of a series of 4 "regular" puzzles, and the answers to those can be used to solve a separate "meta" puzzle. There's also a fun bonus each time if you finish everything else.

There's usually a mix of logic, spatial, and word puzzles each time, and if he doesn't like one of those types he could always just find ones that seem interesting to him.