You could look for a math history book (such as "An Imaginary Tale" by Nahin) or...

chess19 on Aug 10, 2018 | parent | context | favorite | on: A Visual, Intuitive Guide to Imaginary Numbers (20...

You could look for a math history book (such as "An Imaginary Tale" by Nahin) or something like the Princeton Companion to Mathematics or frankly any other popular math book written by established mathematicians.