Category Theory Illustrated: From Sets to Categories
abuseofnotation.github.ioThe book itself is five hundred pages. Printed double-sided and two a page, it's manageable.
Improvements would be to have page numbers in the table of contents instead of blue hyperlinks; an index in the back instead of a repeated ToC; and some minor typos like `&emdash', `f $' as a notation, and `{: definition' text.
Sharper illustrations, too: at standard quality, some of the text in figures need some squinting.
It's an exciting work because between Visual Category Theory Brick by Brick and its reading lists, Category Theory Illustrated promises to fulfill the author's intent to "stay in the middle of the spectrum."