This book is very well written. It does not lack examples to illustrate the theory although some knowledge of advanced mathematics (by advanced I mean for example group theory) is required to understand them. But as I see it this is nothing negative. After all the book is titled "Categories for the Working Mathematician" and not "Categories for Everyone".
Die Kindle-Ausgabe enthält ab Abschnitt IV.1 (Monads) zahlreiche Stellen, wo statt einer Formel nur "image" steht. Sie ist daher in weiten Bereichen **unbrauchbar**. Hoffentlich wird dies schnell korrigiert!
I read this due to its odd title. It is fairly easy to understand. It assumes that you have very little previous knowledge of the subject. For me it just wasn't that useful. Perhaps I was hindered by the fact that I'm not a working mathematician. If you are a mthematics student it is probably a worthwhile read. If not, go for something else.