Best Playbook/guide you have come across?

I started building out my newsletter on Substack (https://ianwdj.substack.com) and want to create some playbooks for how I approach user research. What's the best playbook or guide you have come across and why was it the best for you? Also if you have made one of these before would love to learn about how you went about it? Update: Love the responses! For the builders of playbooks Do you measure success i.e. the user got value from the playbook? If yes, how? What tools are you using to create and manage them? For the consumers of playbooks What do you wish was different? Do you prefer playbooks to have just text, video, audio or a mix of all?