If you're not a mathematician, this reading will be brutal. It will make you feel extremely dumb. I am a programmer, I love functional programming and I wanted to get into category theory and the first few pages were very insightful, but it got extremely complex extremely quickly and I got completely lost around the middle of the book. Didn't finish. Plan to return to it in the near future and give it a second attempt. This is not meant as a criticism. You probably cannot find a more ease-to-read book about category theory. The concept is simply that complicated.