This is a bit of an odd suggestion, but I learned the basics of category theory from the appendix to Weibel’s “An Introduction to Homological Algebra”.
I’m not sure why, but I think the fact that it’s an appendix meant the author had no motivation to inflate the content unnecessarily. So it’s more like a pamphlet; only about 30 pages IIRC, and it’s really just the bare-bones definitions and facts. The full-on textbooks dedicated to category theory have way too much superfluous content IMO, unless your aim is to be a researcher in that field specifically.
This happens a lot! For example, at the appendix of an advanced book on PDE (e.g. Evans') you find a three-page summary of main definitions and results in integration theory and L^p spaces. Or at the appendix of a book on differential geometry (e.g. do Carmo's) you find a succinct compendium of elementary differential calculus, explained in the most efficient way. These kind of condensed summaries, or fascicules de résultats, are rarely found on books that deal with the subject matter directly.
I’m not sure why, but I think the fact that it’s an appendix meant the author had no motivation to inflate the content unnecessarily. So it’s more like a pamphlet; only about 30 pages IIRC, and it’s really just the bare-bones definitions and facts. The full-on textbooks dedicated to category theory have way too much superfluous content IMO, unless your aim is to be a researcher in that field specifically.