Seth Godin is the most practical marketing mentor an indie developer can learn from. His core frameworks — smallest viable audience, permission marketing, ship every day — have clear action paths and require no team or budget. His limitation: 22 years of writing momentum and publishing connections are non-replicable first-mover advantages. But his thinking is 100% learnable and especially suited for one-person companies — because he himself is one of the most successful one-person companies ever. If you read one book, read This Is Marketing (2018).