Rational Points on Elliptic Curves (Undergraduate Texts in Mathematics)

For anyone looking to learn more about elliptic curves, which are astoundingly "well-connected" as math topics go, here's a good book that should be accessible to anyone with some calculus under their belt:

https://www.amazon.com/Elliptic-Tales-Curves-Counting-Number...

It's not a textbook, which is both good and bad. In my case, it did a good job whetting my appetite for more!

A really well-written and not-extremely-difficult undergrad textbook on elliptic curves:

https://www.amazon.com/Rational-Points-Elliptic-Undergraduat...

(Non-affiliate links, just so you know.)