I found a used copy of Category Theory for Programmers by Bartosz Milewski at Half Price Books so I started reading it. If anyone wants to discuss it, we can use this thread.
YouTube playlist of the lectures:
More places to get a copy:
The author also answers questions on Quora:
https://www.quora.com/profile/Bartosz-Milewski
I’m only 30 pages into the book and don’t have an opinion yet.