All these books are in English and focus on the US. If anybody would like to suggest great books in German or other languages, I'd love to add them.
Thinking About Product Design
- Don't Make Me Think, by Steve Krug (2005)
- Badass: Making Users Awesome, by Kathy Sierra (2015)
- The Design of Everyday Things, by Donald Norman (1988)
User Research
- UX for Lean Startups: Faster, Smarter Research and Design, by Laura Klein (2013)
- Lean Customer Development, by Cindy Alvarez (2014)
Content and IA
- Information Architecture, by Peter Morville, Louis Rosenfeld, Jorge Arango (2014)
- Nicely Said: Writing for the Web with Style and Purpose, by Nicole Fenton & Kate Kiefer Lee (2014)
- Communicating Design: Developing Website Documentation for Design and Planning, by Dan M. Brown (2010)
Interface Design
- Designing Interfaces, by Jenifer Tidwell (2011)
- Web Form Design: Filling In the Blanks, by Luke Wroblewski (2008)
- Mobile Design Pattern Gallery, by Theresa Neil (2014)
- Microinteractions, by Dan Saffer (2013)