Best Practices for Game Save Systems

For roguelikes I'd go with JSON but with delta saving — only serialize what changed from the default state. Keeps files small and readable.

Also, always version your save format from day one. Something like:

{
  "version": 2,
  "player": { ... },
  "world": { ... }
}

Then you can write migration functions between versions. Trust me, future you will thank present you.