Book that’s mainly letters or text messages- for a kid

Hey all

I have a really specific ask, I'm hoping you can help. My friend's kid basically only likes to read text/chat messages and video game screens. Kiddo is 9 and doesn't have a phone so this isn't about preferring to chat with friends instead of reading, he just likes to read anyone's text messages.

Is there anything in epistolary style out there for young readers? Or even partially in chat form would be good.