I've seen a lot of great examples about game development from indie games' developer, on iLogos resource ( here: https://www.ilogos.biz/ ), with all the games they have made, and what exact solutions have helped them to improve gameplay in each game. It's pretty important to share an experience...
I would buy something like this, but only if they would make something digital-related, not just with texts and images, but also with explaining videos, with all the steps, which help them to develop game levels and implement different dev solutions.