An you will have to face it, respond to complaints or respond to dozens of e-mails "where can I find information about this and how to do that" and wonder why customers do not come back for more products. If this is your case and you do not know how to effectively convey your specialist knowledge, it is worth digging into topics related to adult learning and preparing your product in accordance with this knowledge.
A good course or e-book does not contain all the knowledge about a given issue. A good product conveys exactly as much knowledge as the phone number list recipient needs to achieve the goal he had in mind when he decided to purchase it. A good product is one that allows the recipient to go through a certain transformation from point A to point.
An it is the creator's role to design an educational process that will lead him through this transformation. For this to happen, you need to know where your recipient is now, where they are going, what they have already tried to achieve it and what resources they have at their disposal, as well as at what stage their knowledge in a given area is currently.