How to modify this page so that the “reading area” should be the size when it is first opened?

  node.js, question
  1. Describe your problem

Our website is: qingyunyuedu.aliapp.com

Now every time I enter, I can only open the content after loading because the loaded books are relatively large. The loading method is completed in iframe inside. The boss asked me to do a good job in this place. The area outside the guarantee has not been loaded. What should I do? Thank you very much

  1. Attach relevant codes

  2. Post error message

  3. Attach relevant screenshots

  4. What methods have been tried and still have not been solved (with relevant links attached)

Add height to outer div