A gentle introduction?
My Category Theory: A Gentle Introduction is intended to be relatively accessible; in particular, it presupposes rather less mathematical background than some texts on categories. The version of January 29, 2018 is x + 291 pp. long, and is very much work-in-slow-progress, at an uneven level. I then had to leave it on the back burner while finishing of IFL2 for the press: but I now hope to return to it.
The current version incorporates a raft of corrections of the previous version, but everything of course still comes with the warning caveat lector. However, although I started writing really as an exercise in getting myself a bit clearer about some basic category theory, I hope that others will find something of interest and use here. Obviously I’d very much welcome comments and corrections.
There are a lot of possible follow-up materials listed here. But if you want something just a step or two up from my notes but still tolerably gentle, let me highlight two books listed below. One is Steve Awodey’s Category Theory (chapters available on his website here). The other is Tom Leinster’s Basic Category Theory.