Undoubtedly I prefer new books. I like the smell of fresh published papers and I can take down my thoughts freely as there’re enough space. Besides, new books are generally the most updated version with less mistakes and new concepts. This is essential when choosing reference books. It’s true that used books are environmental-friendly. But since it’s used, I feel like it’s not mine. also, there may be full of marks and they may disrupt you to generate your own thoughts. And to be honest, the reading process may be unenjoyable.
New books