Dear Peter, Although not exactly a textbook, I could see the Clowder Project providing some amount of value as a reference: https://www.clowderproject.com/. This is a wiki and reference work on category theory I've been working on. It's meant essentially as a Stacks Project for category theory. While it's by all means not a textbook, I've taken care to include as much detail as I can in the exposition, being sure to fill in details that are often left unwritten in articles/books/etc, so perhaps it could still be of some use. Best wishes, Emily On Fri, 11 Jul 2025 at 09:26, Peter Smith <peter_smith@mac.com<mailto:peter_smith@mac.com>> wrote: Dear all, Just to say that I’ve again updated my web-page linking to online materials on category theory, freely/legally available at a more or less introductory level: https://www.logicmatters.net/categories This is visited surprisingly often — about 3K times a month — so I feel I ought to try to keep it in good order! So do please let me know of any recent materials at the same level that I might helpfully add to the lists. And perhaps, when appropriate, spread the word to students who could find the page useful. There is a link to a new version my Introducing Category Theory. I make no claim at all for these notes other than they should be a-bit-more-than-averagely accessible for self-study, and so they might make for helpful preliminary reading for students about to take on an industrial-strength course next term/semester. (I’m quite certainly no category theorist, just a logician of sorts looking with interest over the fence: so I’d of course like to know about any foul-ups, and to have suggestions for improvement!) Kind regards Peter S. Dr Peter Smith www.logicmatters.net You're receiving this message because you're a member of the Categories mailing list group from Macquarie University. To take part in this conversation, reply all to this message. View group files | Leave group | Learn more about Microsoft 365 Groups You're receiving this message because you're a member of the Categories mailing list group from Macquarie University. To take part in this conversation, reply all to this message. View group files<https://outlook.office365.com/owa/categories@mq.edu.au/groupsubscription.ashx?source=EscalatedMessage&action=files&GuestId=6bf90c14-94d1-45b7-a0b5-9dd447734d27> | Leave group<https://outlook.office365.com/owa/categories@mq.edu.au/groupsubscription.ashx?source=EscalatedMessage&action=leave&GuestId=6bf90c14-94d1-45b7-a0b5-9dd447734d27> | Learn more about Microsoft 365 Groups<https://aka.ms/o365g>