Our 13yo is really enjoying designing and building games using Game Maker - both personally, and as school projects.
Any advice from game designers here for some books? He's smart and an advanced reader (but of course I'm biased 馃ぉ) so doesn't have to be anything "aimed at kids" - just "aimed at beginner game designers".
I can help with the programming part of it ... but I've only ever done the one game myself (an IF title using Inform), so I'm essentially entirely clueless when it comes to the game design part.