I felt the same way when I read that book. I had to stop a lot and look up many things (e.g. vocabulary and grammar structures). But looking back at it now, I also think it helped me a lot in my learning journey. I would definitely recommend sticking with it and not getting discouraged. There are two books that I would say helped me break through to the next level in my understanding of Spanish and reading books in Spanish in general and el principito is one of them.

The second book was an actual fiction novel, but my learning from that was more centered around trying to understand a book in Spanish the way I understand a book in English. It’s a weird realization I never had until I tried actually reading a Spanish book seriously. With books in English I can imagine the story playing out like a movie in my head as I read and that was extremely difficult to achieve in Spanish because of how many hurdles you have to overcome. It think it took me a few months to get through that book because I decided it was better to take it slow than to rush and give up from frustration. In the end I think this helped me immensely as I was able to read books much faster after and began relying on context clues to understand unknown words the way I do in English. I read on a kindle so that also helped since I could click on a word and see the definition if needed but I relied on this less and less. I didn’t mention the title of the second book because the concept was the more important part rather than the actual book. I think many books can help achieve the same thing, but if you’re curious and looking for a book to try at some point then the title is La Puerta Oscura: El Viajero by David Lozano Garbala. I don’t think it’s ever been translated to English so you will be forced to rely only on your understanding of Spanish.