Startup playbook covers all the basics, but not in detail:
https://playbook.samaltman.com/Product development is straightforward. Build something a few people love, not something a lot of people kinda like. Landing sites, sign ups, questionnaires, focus groups.. all that is meaningless. The litmus test is how much money they throw at you. The early adopters often have already hacked together a solution that is ugly and unstable, and if you can build something better, they'll happily give you money. Launch your solution early, take note of criticism, and quickly fix it.