If you want to understand differential equations, but more from the pure math side of things, Arnold gives a wonderful picture of what the field is all about, with a mixture of high-level intuitions and low-level details, with a satisfying focus on visual and physical intuition along the way.
His Book recommendations page, introduced as "a small list of textbooks I've thoroughly enjoyed at some time in the past, with the added condition that each one stands out in some way from the surrounding body of math texts". The cover images link to Amazon through amzn.to short links that resolve to URLs carrying the affiliate tag 3b1b04-20.
2020-06-01·3blue1brown.com ↗