The Design of Everyday Things

On the shelf because of one problem: the janitor.

It patrols this demo and puts back what visitors take away, and the first version did it correctly and instantly — which read as a bug. Text reappeared with no cause a visitor could see, so the obvious conclusion was that their edit had failed rather than that something had deliberately reverted it.

The fix is an affordance, not an algorithm

It now moves a cursor, selects the paragraph, and types the old words back at human speed with the occasional typo. Nothing about the outcome changed. Everything about whether it is believable did — which is this book's whole argument, arriving about forty years late.