Most of the techniques showcased in Designing Interfaces will have been seen (not necessarily noticed!) by anyone who spends a lot of time on their computer, but it’s useful to have them all concentrated and organised in one place, so you can see alternatives to the “obvious” design paradigm you’re contemplating at the moment. Tidwell also adds lots of examples and analysis to really give a boost to your understanding.

For example, the first chapter on “user patterns” (descriptions of human behaviour) is a sort of “principles of usability” list that is worth the price of admission. They are:

• safe exploration: support undo!
• instant gratification: why do I have to register before I can try ANYTHING?
• satisficing: people will take the first path they find to get to their destination, even if there’s another more hidden way. They probably won’t RTFM.
• changes in midstream: people routinely abandon things midway.
• deferred choices: don’t make people decide everything upfront, especially when they might not know yet what they want. Let them choose later.
• incremental construction: people iterate to create. Help them. Don’t make them wait ages before they can see what impact a change makes.
• habituation: people do fall into familiar patterns of doing things. Keep things constant to support habituation if that improves efficiency. If you want them to actually think, you’ll have to get creative.
• spatial memory: people remember things based on where they were, so moving things around isn’t that great an idea.
• prospective memory: e.g. reminders, etc. Not often used in
  interface design (except in bookmarks, comments, etc) but worth
  contemplating for inclusion.
• streamlined repetition: don’t bore your user.
• keyboard only: don’t make them use the mouse if possible.
• other people’s advice: people like hearing it and will place more value on it than most anything else – so make your application social if possible.

The actual design patterns are organised into categories like information architecture, navigation, page layout, actions and commands, information graphics, form design, editor design and visual style.

Overall a useful book for inspiration and reference.