This problem, I think. The books you sell should have a specific group! On the one hand, you should strengthen your language learning; On the other hand, you should make an in-depth investigation of your specific customer groups. Every time you sell, you should analyze why you buy it and why you don't buy it. You have to sum it up. There are sales methods, it depends on how you operate! The method we are talking about is to analyze the psychology of customers! Analyze the merits of your book to him. Especially in terms of hobbies! I wish you success!