
In An Imaginary Tale, Paul Nahin tells the 2000-year-old history of one of mathematics' most elusive numbers, the square root of minus one, also known as i, re-creating the baffling mathematical problems that conjured it up and the colorful characters who tried to solve them. Addressing readers with both a general and scholarly interest in mathematics, Nahin weaves into this narrative entertaining historical facts, mathematical discussions, and the application of complex numbers and functions to important problems.
There is a really great book on the history of imaginary numbers. The history mostly focuses on how i was used to help solve algebra problems, so definitely one should be comfortable with high school algebra to get something from the text, but I don't think one needs much more math than that for the first half of the book. The second half gets more into how various use cases developed, in those chapters basic college level calculus would be a major plus. I read it more than 10 years ago though so no promises. :)
An Imaginary Tale: The Story of √-1 Paul J. Nahin
https://press.princeton.edu/books/paperback/9780691169248/an...
Zero: The Biography of a Dangerous Idea - Charles Seife
Measurement - Paul Lockhart
Prelude to Mathematics - W. W. Sawyer
Proofs from The Book - Aigner and Ziegler
The Joy of x - Steven Strogatz
Things to Make and Do in the Fourth Dimension - Matt Parker
What is Mathematics? - Courant and Robbins
A History of PI - Petr Beckmann
An Imaginary Tale - Paul Nahin
e: The Story of a Number - Eli Maor
Imagining Numbers - Barry Mazur
Journey Through Genius - William Dunham
Prime Obsession - John Derbyshire
For Linear Algebra, "Linear Algebra Done Right" -- way better than my college lin alg course.
For "general mathematics", I like books that read almost like novels to really grasp the "why" of mathematics, so these are more to embellish your general understanding of "what is the point" type questions -- so things here like Euclid's Window come to mind, and "An Imaginary Tale: The story of square root minus one" will help explain complex numbers in more detail than you ever cared. Reading about the history of mathematics and the writings of some of the greats, like Rene Descartes, Lehonard Euler, Gottfried Wilhelm Leibniz, Issac Newton (the amazing thing is all these greats lived within a century of each other)