I had a question for y'all. I'm currently an undergrad studying engineering in college (sophomore year) and the current topic of my maths class is partial differential equations. I'm gonna major in computer science, but would like to minor in applied math. However, I have a great interest in pure math, and the subject of pde's really interests me. The "recommended" book for the course is Haberman's book on pde's, but I read online that it's specifically for undergrad students, and that doesn't feel like enough of a challenge to me (to be clear, I don't want to get a book because I feel like I'm struggling to understand what is being taught, but because the subject really tickles my fancy and I want to push it further than what is being taught in my class). On top of that, I also looked up the classes I'll have later down the line and those seem to have a decent amount of pde's in them too. I heard Taylor's book and Evans' book are the go-to choices for a graduate level, and so I was thinking about getting one of those perhaps, but I'd like some advice from y'all before doing that as these books are pretty expensive and I don't want to splash 150$ on a book that I can't enjoy.
That being said, I am looking for a challenge, so if I would need to teach myself some other stuff in math (as long as it's not too hard to learn by myself of course) to be able to understand the harder texts on those books, then that's fine.
I am also aware of various pdfs of these books but I don't know how I feel about not giving the author their well-earned reward when reading a book.
Thanks in advance!