Teacher Diego and Tristan are correct. I looked up Chapter 11. The conceited man wanted the little prince's admiration, so the little prince said the words that the conceited man wanted to hear. However, he didn't understand WHY being admired was so important to the conceited man. So he asked him WHY, stated differently. "What is there in that to interest you so much?" What is there, in my admiring you, that means so much to you? How come you need me to admire you? Hope this was helpful! :)

Hello!!! "In that" in this context refers to the topic or subject they are talking about. For example, if we are talking about classical music and you say you love it, but i don't, i would ask you something like ¿what is there "in that" (refering to classical music) you love so much? Hope this exapmple really helps you understand it better. Have a great day!!

"But what is there in, the (science), to interest you so much?" When the author says "that", they are referring to a specific thing. Replace "science" with whatever the author is talking about. I hope this helps! (It is a kind of hard concept to explain)

Thank you, Alan! That's worth knowing. I have taken down what you said!

Just a quick note: "besides" doesn't mean what most Chinese speakers think it means. It doesn't really mean "moreover", its meaning is closer to "anyway". Examples: "I don't want to go running today because it's raining. Besides, I'm too tired." "I don't think I need to study for the test, it'll be easy. Besides, it's just a practice test." "Besides" is usually used to add an extra, unimportant detail. It's certainly not used to change the topic.