Don't let the "Things" in the title fool you. The basic principles of design explored by Donald Norman apply as much to services and interactions as they do to products (which are the main focus of this book, originally published in 1988).

I basically use the main ideas in the book as a checklist, to make sure that the interaction we are designing is as intuitive as possible for the user (i.e. providing feedback — is the result of an action taken by the user always visible to her?).